<?xml version="1.0" encoding="us-ascii"?>
<!-- DFIN ActiveDisclosure(SM) XBRL Linkbase Document - http://www.dfinsolutions.com/ -->
<!-- Creation Date      : 2021-03-15T19:14:15.6912642+00:00 -->
<!-- Version            : 5.0.1.571 -->
<!-- Package ID         : a21ea12e5d3f49d09a8eecb21a1e9c87 -->
<!-- Copyright (c) 2021 Donnelley Financial Solutions, Inc. All Rights Reserved. -->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:roleRef xlink:type="simple" xlink:href="fusb-20201231.xsd#TemplateLink" roleURI="http://www.firstusbank.com/20201231/role/TemplateLink" />
  <link:roleRef roleURI="http://www.firstusbank.com/20201231/taxonomy/role/StatementConsolidatedBalanceSheets" xlink:href="fusb-20201231.xsd#Role_StatementConsolidatedBalanceSheets" xlink:type="simple" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.firstusbank.com/20201231/taxonomy/role/StatementConsolidatedBalanceSheets">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestBearingDepositsInBanks" xlink:type="locator" xlink:label="us-gaap_InterestBearingDepositsInBanks" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashAndDueFromBanks" xlink:type="locator" xlink:label="us-gaap_CashAndDueFromBanks" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherAssets" xlink:type="locator" xlink:label="us-gaap_OtherAssets" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RealEstateAcquiredThroughForeclosure" xlink:type="locator" xlink:label="us-gaap_RealEstateAcquiredThroughForeclosure" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IntangibleAssetsNetIncludingGoodwill" xlink:type="locator" xlink:label="us-gaap_IntangibleAssetsNetIncludingGoodwill" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestReceivable" xlink:type="locator" xlink:label="us-gaap_InterestReceivable" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BankOwnedLifeInsurance" xlink:type="locator" xlink:label="us-gaap_BankOwnedLifeInsurance" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentNet" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LoansAndLeasesReceivableNetReportedAmount" xlink:type="locator" xlink:label="us-gaap_LoansAndLeasesReceivableNetReportedAmount" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FederalHomeLoanBankStock" xlink:type="locator" xlink:label="us-gaap_FederalHomeLoanBankStock" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_HeldToMaturitySecurities" xlink:type="locator" xlink:label="us-gaap_HeldToMaturitySecurities" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:type="locator" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FederalFundsSold" xlink:type="locator" xlink:label="us-gaap_FederalFundsSold" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:type="locator" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Assets" xlink:type="locator" xlink:label="us-gaap_Assets" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestBearingDepositLiabilities" xlink:type="locator" xlink:label="us-gaap_InterestBearingDepositLiabilities" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NoninterestBearingDepositLiabilities" xlink:type="locator" xlink:label="us-gaap_NoninterestBearingDepositLiabilities" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShortTermBorrowings" xlink:type="locator" xlink:label="us-gaap_ShortTermBorrowings" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherLiabilities" xlink:type="locator" xlink:label="us-gaap_OtherLiabilities" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DepositLiabilitiesAccruedInterest" xlink:type="locator" xlink:label="us-gaap_DepositLiabilitiesAccruedInterest" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Deposits" xlink:type="locator" xlink:label="us-gaap_Deposits" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TreasuryStockValue" xlink:type="locator" xlink:label="us-gaap_TreasuryStockValue" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:type="locator" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:type="locator" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdditionalPaidInCapitalCommonStock" xlink:type="locator" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockValue" xlink:type="locator" xlink:label="us-gaap_CommonStockValue" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" xlink:type="locator" xlink:label="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Liabilities" xlink:type="locator" xlink:label="us-gaap_Liabilities" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:type="locator" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_LiabilitiesAndStockholdersEquity" xlink:to="us-gaap_Liabilities" order="10010.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_LiabilitiesAndStockholdersEquity" xlink:to="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" order="10020.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" xlink:to="us-gaap_CommonStockValue" order="10030.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" xlink:to="us-gaap_AdditionalPaidInCapitalCommonStock" order="10040.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" xlink:to="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" order="10050.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" xlink:to="us-gaap_RetainedEarningsAccumulatedDeficit" order="10060.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" xlink:to="us-gaap_TreasuryStockValue" order="10070.00" priority="2" use="optional" weight="-1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Liabilities" xlink:to="us-gaap_Deposits" order="10080.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Liabilities" xlink:to="us-gaap_DepositLiabilitiesAccruedInterest" order="10090.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Liabilities" xlink:to="us-gaap_OtherLiabilities" order="10100.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Liabilities" xlink:to="us-gaap_ShortTermBorrowings" order="10110.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Deposits" xlink:to="us-gaap_NoninterestBearingDepositLiabilities" order="10120.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Deposits" xlink:to="us-gaap_InterestBearingDepositLiabilities" order="10130.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Assets" xlink:to="us-gaap_CashAndCashEquivalentsAtCarryingValue" order="10140.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Assets" xlink:to="us-gaap_FederalFundsSold" order="10150.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Assets" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtSecurities" order="10160.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Assets" xlink:to="us-gaap_HeldToMaturitySecurities" order="10170.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Assets" xlink:to="us-gaap_FederalHomeLoanBankStock" order="10180.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Assets" xlink:to="us-gaap_LoansAndLeasesReceivableNetReportedAmount" order="10190.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Assets" xlink:to="us-gaap_PropertyPlantAndEquipmentNet" order="10200.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Assets" xlink:to="us-gaap_BankOwnedLifeInsurance" order="10210.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Assets" xlink:to="us-gaap_InterestReceivable" order="10220.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Assets" xlink:to="us-gaap_IntangibleAssetsNetIncludingGoodwill" order="10230.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Assets" xlink:to="us-gaap_RealEstateAcquiredThroughForeclosure" order="10240.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Assets" xlink:to="us-gaap_OtherAssets" order="10250.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:to="us-gaap_CashAndDueFromBanks" order="10260.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:to="us-gaap_InterestBearingDepositsInBanks" order="10270.00" priority="2" use="optional" weight="1.00" />
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstusbank.com/20201231/taxonomy/role/StatementConsolidatedStatementsOfOperations" xlink:href="fusb-20201231.xsd#Role_StatementConsolidatedStatementsOfOperations" xlink:type="simple" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.firstusbank.com/20201231/taxonomy/role/StatementConsolidatedStatementsOfOperations">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestAndDividendIncomeSecuritiesOther" xlink:type="locator" xlink:label="us-gaap_InterestAndDividendIncomeSecuritiesOther" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestIncomeSecuritiesTaxExempt" xlink:type="locator" xlink:label="us-gaap_InterestIncomeSecuritiesTaxExempt" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestIncomeSecuritiesTaxable" xlink:type="locator" xlink:label="us-gaap_InterestIncomeSecuritiesTaxable" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestAndFeeIncomeLoansAndLeases" xlink:type="locator" xlink:label="us-gaap_InterestAndFeeIncomeLoansAndLeases" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestExpenseShortTermBorrowings" xlink:type="locator" xlink:label="us-gaap_InterestExpenseShortTermBorrowings" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestExpenseDeposits" xlink:type="locator" xlink:label="us-gaap_InterestExpenseDeposits" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestExpense" xlink:type="locator" xlink:label="us-gaap_InterestExpense" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestAndDividendIncomeOperating" xlink:type="locator" xlink:label="us-gaap_InterestAndDividendIncomeOperating" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProvisionForLoanLeaseAndOtherLosses" xlink:type="locator" xlink:label="us-gaap_ProvisionForLoanLeaseAndOtherLosses" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestIncomeExpenseNet" xlink:type="locator" xlink:label="us-gaap_InterestIncomeExpenseNet" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NoninterestIncomeOther" xlink:type="locator" xlink:label="us-gaap_NoninterestIncomeOther" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LeaseIncome" xlink:type="locator" xlink:label="us-gaap_LeaseIncome" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleRealizedGainLoss" xlink:type="locator" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleRealizedGainLoss" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InsuranceCommissionsAndFees" xlink:type="locator" xlink:label="us-gaap_InsuranceCommissionsAndFees" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax" xlink:type="locator" xlink:label="us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherNoninterestExpense" xlink:type="locator" xlink:label="us-gaap_OtherNoninterestExpense" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProfessionalFees" xlink:type="locator" xlink:label="us-gaap_ProfessionalFees" />
    <link:loc xlink:href="fusb-20201231.xsd#fusb_ComputerServicesExpense" xlink:type="locator" xlink:label="fusb_ComputerServicesExpense" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OccupancyNet" xlink:type="locator" xlink:label="us-gaap_OccupancyNet" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LaborAndRelatedExpense" xlink:type="locator" xlink:label="us-gaap_LaborAndRelatedExpense" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NoninterestExpense" xlink:type="locator" xlink:label="us-gaap_NoninterestExpense" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NoninterestIncome" xlink:type="locator" xlink:label="us-gaap_NoninterestIncome" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss" xlink:type="locator" xlink:label="us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:type="locator" xlink:label="us-gaap_IncomeTaxExpenseBenefit" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:type="locator" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetIncomeLoss" xlink:type="locator" xlink:label="us-gaap_NetIncomeLoss" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetIncomeLoss" xlink:to="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" order="10010.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetIncomeLoss" xlink:to="us-gaap_IncomeTaxExpenseBenefit" order="10020.00" priority="2" use="optional" weight="-1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:to="us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss" order="10030.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:to="us-gaap_NoninterestIncome" order="10040.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:to="us-gaap_NoninterestExpense" order="10050.00" priority="2" use="optional" weight="-1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NoninterestExpense" xlink:to="us-gaap_LaborAndRelatedExpense" order="10060.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NoninterestExpense" xlink:to="us-gaap_OccupancyNet" order="10070.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NoninterestExpense" xlink:to="fusb_ComputerServicesExpense" order="10080.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NoninterestExpense" xlink:to="us-gaap_ProfessionalFees" order="10090.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NoninterestExpense" xlink:to="us-gaap_OtherNoninterestExpense" order="10100.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NoninterestIncome" xlink:to="us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax" order="10110.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NoninterestIncome" xlink:to="us-gaap_InsuranceCommissionsAndFees" order="10120.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NoninterestIncome" xlink:to="us-gaap_DebtSecuritiesAvailableForSaleRealizedGainLoss" order="10130.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NoninterestIncome" xlink:to="us-gaap_LeaseIncome" order="10150.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NoninterestIncome" xlink:to="us-gaap_NoninterestIncomeOther" order="10160.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss" xlink:to="us-gaap_InterestIncomeExpenseNet" order="10170.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss" xlink:to="us-gaap_ProvisionForLoanLeaseAndOtherLosses" order="10180.00" priority="2" use="optional" weight="-1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InterestIncomeExpenseNet" xlink:to="us-gaap_InterestAndDividendIncomeOperating" order="10190.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InterestIncomeExpenseNet" xlink:to="us-gaap_InterestExpense" order="10200.00" priority="2" use="optional" weight="-1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InterestExpense" xlink:to="us-gaap_InterestExpenseDeposits" order="10210.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InterestExpense" xlink:to="us-gaap_InterestExpenseShortTermBorrowings" order="10220.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InterestAndDividendIncomeOperating" xlink:to="us-gaap_InterestAndFeeIncomeLoansAndLeases" order="10230.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InterestAndDividendIncomeOperating" xlink:to="us-gaap_InterestIncomeSecuritiesTaxable" order="10240.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InterestAndDividendIncomeOperating" xlink:to="us-gaap_InterestIncomeSecuritiesTaxExempt" order="10250.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InterestAndDividendIncomeOperating" xlink:to="us-gaap_InterestAndDividendIncomeSecuritiesOther" order="10260.00" priority="2" use="optional" weight="1.00" />
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstusbank.com/20201231/taxonomy/role/StatementConsolidatedStatementsOfComprehensiveIncomeLoss" xlink:href="fusb-20201231.xsd#Role_StatementConsolidatedStatementsOfComprehensiveIncomeLoss" xlink:type="simple" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.firstusbank.com/20201231/taxonomy/role/StatementConsolidatedStatementsOfComprehensiveIncomeLoss">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax" xlink:type="locator" xlink:label="us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax" xlink:type="locator" xlink:label="us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax" xlink:type="locator" xlink:label="us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:type="locator" xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTax" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProfitLoss" xlink:type="locator" xlink:label="us-gaap_ProfitLoss" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest" xlink:type="locator" xlink:label="us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest" xlink:to="us-gaap_ProfitLoss" order="10010.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest" xlink:to="us-gaap_OtherComprehensiveIncomeLossNetOfTax" order="10020.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:to="us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax" order="10030.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:to="us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax" order="10040.00" priority="2" use="optional" weight="-1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:to="us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax" order="10050.00" priority="2" use="optional" weight="1.00" />
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstusbank.com/20201231/taxonomy/role/StatementConsolidatedStatementsOfCashFlows" xlink:href="fusb-20201231.xsd#Role_StatementConsolidatedStatementsOfCashFlows" xlink:type="simple" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.firstusbank.com/20201231/taxonomy/role/StatementConsolidatedStatementsOfCashFlows">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInOtherOperatingLiabilities" xlink:type="locator" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingLiabilities" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInInterestPayableNet" xlink:type="locator" xlink:label="us-gaap_IncreaseDecreaseInInterestPayableNet" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInOtherOperatingAssets" xlink:type="locator" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingAssets" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet" xlink:type="locator" xlink:label="us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet" />
    <link:loc xlink:href="fusb-20201231.xsd#fusb_GainsLossesOnSalesOfPremisesEquipmentAndOtherRealEstateHeldForSale" xlink:type="locator" xlink:label="fusb_GainsLossesOnSalesOfPremisesEquipmentAndOtherRealEstateHeldForSale" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AmortizationOfIntangibleAssets" xlink:type="locator" xlink:label="us-gaap_AmortizationOfIntangibleAssets" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AmortizationOfDebtDiscountPremium" xlink:type="locator" xlink:label="us-gaap_AmortizationOfDebtDiscountPremium" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensation" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensation" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleRealizedGainLoss" xlink:type="locator" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleRealizedGainLoss" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredIncomeTaxExpenseBenefit" xlink:type="locator" xlink:label="us-gaap_DeferredIncomeTaxExpenseBenefit" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProvisionForLoanLeaseAndOtherLosses" xlink:type="locator" xlink:label="us-gaap_ProvisionForLoanLeaseAndOtherLosses" />
    <link:loc xlink:href="fusb-20201231.xsd#fusb_DepreciationAndAmortizationOfPropertyPlantAndEquipmentAndComputerPrograms" xlink:type="locator" xlink:label="fusb_DepreciationAndAmortizationOfPropertyPlantAndEquipmentAndComputerPrograms" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProfitLoss" xlink:type="locator" xlink:label="us-gaap_ProfitLoss" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" xlink:type="locator" xlink:label="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsForProceedsFromLoansReceivable" xlink:type="locator" xlink:label="us-gaap_PaymentsForProceedsFromLoansReceivable" />
    <link:loc xlink:href="fusb-20201231.xsd#fusb_ProceedsFromSaleOfPremisesAndEquipmentAndOtherRealEstate" xlink:type="locator" xlink:label="fusb_ProceedsFromSaleOfPremisesAndEquipmentAndOtherRealEstate" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsForProceedsFromFederalHomeLoanBankStock" xlink:type="locator" xlink:label="us-gaap_PaymentsForProceedsFromFederalHomeLoanBankStock" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities" xlink:type="locator" xlink:label="us-gaap_ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities" xlink:type="locator" xlink:label="us-gaap_ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromSaleOfAvailableForSaleSecuritiesDebt" xlink:type="locator" xlink:label="us-gaap_ProceedsFromSaleOfAvailableForSaleSecuritiesDebt" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt" xlink:type="locator" xlink:label="us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInFederalFundsSold" xlink:type="locator" xlink:label="us-gaap_IncreaseDecreaseInFederalFundsSold" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsOfDividends" xlink:type="locator" xlink:label="us-gaap_PaymentsOfDividends" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsForRepurchaseOfCommonStock" xlink:type="locator" xlink:label="us-gaap_PaymentsForRepurchaseOfCommonStock" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromRepaymentsOfShortTermDebt" xlink:type="locator" xlink:label="us-gaap_ProceedsFromRepaymentsOfShortTermDebt" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInContractWithCustomerLiability" xlink:type="locator" xlink:label="us-gaap_IncreaseDecreaseInContractWithCustomerLiability" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:type="locator" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:type="locator" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:type="locator" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:type="locator" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:to="us-gaap_NetCashProvidedByUsedInOperatingActivities" order="10010.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:to="us-gaap_NetCashProvidedByUsedInInvestingActivities" order="10020.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:to="us-gaap_NetCashProvidedByUsedInFinancingActivities" order="10030.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:to="us-gaap_IncreaseDecreaseInContractWithCustomerLiability" order="10040.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:to="us-gaap_ProceedsFromRepaymentsOfShortTermDebt" order="10050.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:to="us-gaap_PaymentsForRepurchaseOfCommonStock" order="10060.00" priority="2" use="optional" weight="-1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:to="us-gaap_PaymentsOfDividends" order="10070.00" priority="2" use="optional" weight="-1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:to="us-gaap_IncreaseDecreaseInFederalFundsSold" order="10080.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:to="us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt" order="10090.00" priority="2" use="optional" weight="-1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:to="us-gaap_ProceedsFromSaleOfAvailableForSaleSecuritiesDebt" order="10100.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:to="us-gaap_ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities" order="10110.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:to="us-gaap_ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities" order="10120.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:to="us-gaap_PaymentsForProceedsFromFederalHomeLoanBankStock" order="10130.00" priority="2" use="optional" weight="-1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:to="fusb_ProceedsFromSaleOfPremisesAndEquipmentAndOtherRealEstate" order="10140.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:to="us-gaap_PaymentsForProceedsFromLoansReceivable" order="10150.00" priority="2" use="optional" weight="-1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:to="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" order="10160.00" priority="2" use="optional" weight="-1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_ProfitLoss" order="10170.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="fusb_DepreciationAndAmortizationOfPropertyPlantAndEquipmentAndComputerPrograms" order="10180.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_ProvisionForLoanLeaseAndOtherLosses" order="10190.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_DeferredIncomeTaxExpenseBenefit" order="10200.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_DebtSecuritiesAvailableForSaleRealizedGainLoss" order="10210.00" priority="2" use="optional" weight="-1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_ShareBasedCompensation" order="10220.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_AmortizationOfDebtDiscountPremium" order="10230.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_AmortizationOfIntangibleAssets" order="10240.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="fusb_GainsLossesOnSalesOfPremisesEquipmentAndOtherRealEstateHeldForSale" order="10250.00" priority="2" use="optional" weight="-1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet" order="10260.00" priority="2" use="optional" weight="-1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_IncreaseDecreaseInOtherOperatingAssets" order="10270.00" priority="2" use="optional" weight="-1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_IncreaseDecreaseInInterestPayableNet" order="10280.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_IncreaseDecreaseInOtherOperatingLiabilities" order="10290.00" priority="2" use="optional" weight="1.00" />
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesBasicAndDilutedNetIncomePerShareDetails" xlink:href="fusb-20201231.xsd#Role_DisclosureSummaryOfSignificantAccountingPoliciesBasicAndDilutedNetIncomePerShareDetails" xlink:type="simple" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesBasicAndDilutedNetIncomePerShareDetails">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment" xlink:type="locator" xlink:label="us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:type="locator" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:type="locator" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:to="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" order="10010.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:to="us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment" order="10020.00" priority="2" use="optional" weight="1.00" />
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureInvestmentSecuritiesAvailableForSaleAndHeldToMaturityDetails" xlink:href="fusb-20201231.xsd#Role_DisclosureInvestmentSecuritiesAvailableForSaleAndHeldToMaturityDetails" xlink:type="simple" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureInvestmentSecuritiesAvailableForSaleAndHeldToMaturityDetails">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:type="locator" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax" xlink:type="locator" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax" xlink:type="locator" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" xlink:type="locator" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_HeldToMaturitySecuritiesFairValue" xlink:type="locator" xlink:label="us-gaap_HeldToMaturitySecuritiesFairValue" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss" xlink:type="locator" xlink:label="us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain" xlink:type="locator" xlink:label="us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_HeldToMaturitySecurities" xlink:type="locator" xlink:label="us-gaap_HeldToMaturitySecurities" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_HeldToMaturitySecurities" xlink:to="us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain" order="10010.00" priority="2" use="optional" weight="-1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_HeldToMaturitySecurities" xlink:to="us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss" order="10020.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_HeldToMaturitySecurities" xlink:to="us-gaap_HeldToMaturitySecuritiesFairValue" order="10030.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" xlink:to="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax" order="10040.00" priority="2" use="optional" weight="-1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" xlink:to="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax" order="10050.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtSecurities" order="10060.00" priority="2" use="optional" weight="1.00" />
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureInvestmentSecuritiesScheduledMaturitiesOfInvestmentSecuritiesAvailableForSaleAndHeldToMaturityDetails" xlink:href="fusb-20201231.xsd#Role_DisclosureInvestmentSecuritiesScheduledMaturitiesOfInvestmentSecuritiesAvailableForSaleAndHeldToMaturityDetails" xlink:type="simple" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureInvestmentSecuritiesScheduledMaturitiesOfInvestmentSecuritiesAvailableForSaleAndHeldToMaturityDetails">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost" xlink:type="locator" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost" xlink:type="locator" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost" xlink:type="locator" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost" xlink:type="locator" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" xlink:type="locator" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue" xlink:type="locator" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue" xlink:type="locator" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue" xlink:type="locator" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue" xlink:type="locator" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:type="locator" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount" xlink:type="locator" xlink:label="us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount" xlink:type="locator" xlink:label="us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount" xlink:type="locator" xlink:label="us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount" xlink:type="locator" xlink:label="us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_HeldToMaturitySecurities" xlink:type="locator" xlink:label="us-gaap_HeldToMaturitySecurities" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue" xlink:type="locator" xlink:label="us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue" xlink:type="locator" xlink:label="us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue" xlink:type="locator" xlink:label="us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue" xlink:type="locator" xlink:label="us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_HeldToMaturitySecuritiesFairValue" xlink:type="locator" xlink:label="us-gaap_HeldToMaturitySecuritiesFairValue" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_HeldToMaturitySecuritiesFairValue" xlink:to="us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue" order="10010.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_HeldToMaturitySecuritiesFairValue" xlink:to="us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue" order="10020.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_HeldToMaturitySecuritiesFairValue" xlink:to="us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue" order="10030.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_HeldToMaturitySecuritiesFairValue" xlink:to="us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue" order="10040.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_HeldToMaturitySecurities" xlink:to="us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount" order="10050.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_HeldToMaturitySecurities" xlink:to="us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount" order="10060.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_HeldToMaturitySecurities" xlink:to="us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount" order="10070.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_HeldToMaturitySecurities" xlink:to="us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount" order="10080.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue" order="10090.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue" order="10100.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue" order="10110.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue" order="10120.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost" order="10130.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost" order="10140.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost" order="10150.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost" order="10160.00" priority="2" use="optional" weight="1.00" />
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureLoansAndAllowanceForLoanAndLeaseLossesScheduleOfLoanPortfolioDetails" xlink:href="fusb-20201231.xsd#Role_DisclosureLoansAndAllowanceForLoanAndLeaseLossesScheduleOfLoanPortfolioDetails" xlink:type="simple" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureLoansAndAllowanceForLoanAndLeaseLossesScheduleOfLoanPortfolioDetails">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LoansAndLeasesReceivableAllowance" xlink:type="locator" xlink:label="us-gaap_LoansAndLeasesReceivableAllowance" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LoansAndLeasesReceivableDeferredIncome" xlink:type="locator" xlink:label="us-gaap_LoansAndLeasesReceivableDeferredIncome" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LoansAndLeasesReceivableGrossCarryingAmount" xlink:type="locator" xlink:label="us-gaap_LoansAndLeasesReceivableGrossCarryingAmount" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LoansAndLeasesReceivableNetReportedAmount" xlink:type="locator" xlink:label="us-gaap_LoansAndLeasesReceivableNetReportedAmount" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_LoansAndLeasesReceivableNetReportedAmount" xlink:to="us-gaap_LoansAndLeasesReceivableGrossCarryingAmount" order="10010.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_LoansAndLeasesReceivableNetReportedAmount" xlink:to="us-gaap_LoansAndLeasesReceivableDeferredIncome" order="10020.00" priority="2" use="optional" weight="-1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_LoansAndLeasesReceivableNetReportedAmount" xlink:to="us-gaap_LoansAndLeasesReceivableAllowance" order="10030.00" priority="2" use="optional" weight="-1.00" />
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureLoansAndAllowanceForLoanAndLeaseLossesSummaryOfAcquiredLoansDetails" xlink:href="fusb-20201231.xsd#Role_DisclosureLoansAndAllowanceForLoanAndLeaseLossesSummaryOfAcquiredLoansDetails" xlink:type="simple" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureLoansAndAllowanceForLoanAndLeaseLossesSummaryOfAcquiredLoansDetails">
    <link:loc xlink:href="fusb-20201231.xsd#fusb_CertainLoansAcquiredInTransferAccountedForAsDebtSecuritiesFairValueAdjustment" xlink:type="locator" xlink:label="fusb_CertainLoansAcquiredInTransferAccountedForAsDebtSecuritiesFairValueAdjustment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CertainLoansAcquiredInTransferAccountedForAsDebtSecuritiesOutstandingBalance" xlink:type="locator" xlink:label="us-gaap_CertainLoansAcquiredInTransferAccountedForAsDebtSecuritiesOutstandingBalance" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CertainLoansAcquiredInTransferAccountedForAsDebtSecuritiesCarryingAmountNet" xlink:type="locator" xlink:label="us-gaap_CertainLoansAcquiredInTransferAccountedForAsDebtSecuritiesCarryingAmountNet" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_CertainLoansAcquiredInTransferAccountedForAsDebtSecuritiesCarryingAmountNet" xlink:to="us-gaap_CertainLoansAcquiredInTransferAccountedForAsDebtSecuritiesOutstandingBalance" order="10010.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_CertainLoansAcquiredInTransferAccountedForAsDebtSecuritiesCarryingAmountNet" xlink:to="fusb_CertainLoansAcquiredInTransferAccountedForAsDebtSecuritiesFairValueAdjustment" order="10020.00" priority="2" use="optional" weight="1.00" />
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureOtherRealEstateOwnedAndRepossessionsSummaryOfRepossessedAssetsActivityDetails" xlink:href="fusb-20201231.xsd#Role_DisclosureOtherRealEstateOwnedAndRepossessionsSummaryOfRepossessedAssetsActivityDetails" xlink:type="simple" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureOtherRealEstateOwnedAndRepossessionsSummaryOfRepossessedAssetsActivityDetails">
    <link:loc xlink:href="fusb-20201231.xsd#fusb_OtherRealEstateGrossLosses" xlink:type="locator" xlink:label="fusb_OtherRealEstateGrossLosses" />
    <link:loc xlink:href="fusb-20201231.xsd#fusb_OtherRealEstateGrossGains" xlink:type="locator" xlink:label="fusb_OtherRealEstateGrossGains" />
    <link:loc xlink:href="fusb-20201231.xsd#fusb_OtherRealEstateNetIncomeLoss" xlink:type="locator" xlink:label="fusb_OtherRealEstateNetIncomeLoss" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="fusb_OtherRealEstateNetIncomeLoss" xlink:to="fusb_OtherRealEstateGrossGains" order="10010.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="fusb_OtherRealEstateNetIncomeLoss" xlink:to="fusb_OtherRealEstateGrossLosses" order="10020.00" priority="2" use="optional" weight="-1.00" />
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureGoodwillAndOtherIntangibleAssetsSummaryOfGoodwillAndOtherIntangibleAssetsDetails" xlink:href="fusb-20201231.xsd#Role_DisclosureGoodwillAndOtherIntangibleAssetsSummaryOfGoodwillAndOtherIntangibleAssetsDetails" xlink:type="simple" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureGoodwillAndOtherIntangibleAssetsSummaryOfGoodwillAndOtherIntangibleAssetsDetails">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization" xlink:type="locator" xlink:label="us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsGross" xlink:type="locator" xlink:label="us-gaap_FiniteLivedIntangibleAssetsGross" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet" xlink:type="locator" xlink:label="us-gaap_FiniteLivedIntangibleAssetsNet" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Goodwill" xlink:type="locator" xlink:label="us-gaap_Goodwill" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IntangibleAssetsNetIncludingGoodwill" xlink:type="locator" xlink:label="us-gaap_IntangibleAssetsNetIncludingGoodwill" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_IntangibleAssetsNetIncludingGoodwill" xlink:to="us-gaap_Goodwill" order="10010.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_IntangibleAssetsNetIncludingGoodwill" xlink:to="us-gaap_FiniteLivedIntangibleAssetsNet" order="10020.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_FiniteLivedIntangibleAssetsNet" xlink:to="us-gaap_FiniteLivedIntangibleAssetsGross" order="10030.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_FiniteLivedIntangibleAssetsNet" xlink:to="us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization" order="10040.00" priority="2" use="optional" weight="-1.00" />
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureGoodwillAndOtherIntangibleAssetsEstimatedRemainingAmortizationExpenseDetails" xlink:href="fusb-20201231.xsd#Role_DisclosureGoodwillAndOtherIntangibleAssetsEstimatedRemainingAmortizationExpenseDetails" xlink:type="simple" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureGoodwillAndOtherIntangibleAssetsEstimatedRemainingAmortizationExpenseDetails">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive" xlink:type="locator" xlink:label="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour" xlink:type="locator" xlink:label="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree" xlink:type="locator" xlink:label="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo" xlink:type="locator" xlink:label="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths" xlink:type="locator" xlink:label="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet" xlink:type="locator" xlink:label="us-gaap_FiniteLivedIntangibleAssetsNet" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_FiniteLivedIntangibleAssetsNet" xlink:to="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths" order="10010.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_FiniteLivedIntangibleAssetsNet" xlink:to="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo" order="10020.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_FiniteLivedIntangibleAssetsNet" xlink:to="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree" order="10030.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_FiniteLivedIntangibleAssetsNet" xlink:to="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour" order="10040.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_FiniteLivedIntangibleAssetsNet" xlink:to="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive" order="10050.00" priority="2" use="optional" weight="1.00" />
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstusbank.com/20201231/taxonomy/role/DisclosurePremisesAndEquipmentSummaryOfPremisesAndEquipmentAndApplicableDepreciableLivesDetails" xlink:href="fusb-20201231.xsd#Role_DisclosurePremisesAndEquipmentSummaryOfPremisesAndEquipmentAndApplicableDepreciableLivesDetails" xlink:type="simple" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.firstusbank.com/20201231/taxonomy/role/DisclosurePremisesAndEquipmentSummaryOfPremisesAndEquipmentAndApplicableDepreciableLivesDetails">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:type="locator" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentGross" xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentGross" />
    <link:loc xlink:href="fusb-20201231.xsd#fusb_ConstructionInProgressNet" xlink:type="locator" xlink:label="fusb_ConstructionInProgressNet" />
    <link:loc xlink:href="fusb-20201231.xsd#fusb_PropertyPlantAndEquipmentExcludingConstructionInProgressNet" xlink:type="locator" xlink:label="fusb_PropertyPlantAndEquipmentExcludingConstructionInProgressNet" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentNet" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_PropertyPlantAndEquipmentNet" xlink:to="fusb_PropertyPlantAndEquipmentExcludingConstructionInProgressNet" order="10010.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_PropertyPlantAndEquipmentNet" xlink:to="fusb_ConstructionInProgressNet" order="10020.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="fusb_PropertyPlantAndEquipmentExcludingConstructionInProgressNet" xlink:to="us-gaap_PropertyPlantAndEquipmentGross" order="10030.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="fusb_PropertyPlantAndEquipmentExcludingConstructionInProgressNet" xlink:to="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" order="10040.00" priority="2" use="optional" weight="-1.00" />
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureDepositsScheduledMaturitiesOfBankSTimeDepositsDetails" xlink:href="fusb-20201231.xsd#Role_DisclosureDepositsScheduledMaturitiesOfBankSTimeDepositsDetails" xlink:type="simple" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureDepositsScheduledMaturitiesOfBankSTimeDepositsDetails">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TimeDepositMaturitiesYearFive" xlink:type="locator" xlink:label="us-gaap_TimeDepositMaturitiesYearFive" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TimeDepositMaturitiesYearFour" xlink:type="locator" xlink:label="us-gaap_TimeDepositMaturitiesYearFour" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TimeDepositMaturitiesYearThree" xlink:type="locator" xlink:label="us-gaap_TimeDepositMaturitiesYearThree" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TimeDepositMaturitiesYearTwo" xlink:type="locator" xlink:label="us-gaap_TimeDepositMaturitiesYearTwo" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TimeDepositMaturitiesYearOne" xlink:type="locator" xlink:label="us-gaap_TimeDepositMaturitiesYearOne" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TimeDeposits" xlink:type="locator" xlink:label="us-gaap_TimeDeposits" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_TimeDeposits" xlink:to="us-gaap_TimeDepositMaturitiesYearOne" order="10010.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_TimeDeposits" xlink:to="us-gaap_TimeDepositMaturitiesYearTwo" order="10020.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_TimeDeposits" xlink:to="us-gaap_TimeDepositMaturitiesYearThree" order="10030.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_TimeDeposits" xlink:to="us-gaap_TimeDepositMaturitiesYearFour" order="10040.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_TimeDeposits" xlink:to="us-gaap_TimeDepositMaturitiesYearFive" order="10050.00" priority="2" use="optional" weight="1.00" />
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureIncomeTaxesConsolidatedProvisionForIncomeTaxesDetails" xlink:href="fusb-20201231.xsd#Role_DisclosureIncomeTaxesConsolidatedProvisionForIncomeTaxesDetails" xlink:type="simple" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureIncomeTaxesConsolidatedProvisionForIncomeTaxesDetails">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredFederalIncomeTaxExpenseBenefit" xlink:type="locator" xlink:label="us-gaap_DeferredFederalIncomeTaxExpenseBenefit" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CurrentFederalTaxExpenseBenefit" xlink:type="locator" xlink:label="us-gaap_CurrentFederalTaxExpenseBenefit" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredStateAndLocalIncomeTaxExpenseBenefit" xlink:type="locator" xlink:label="us-gaap_DeferredStateAndLocalIncomeTaxExpenseBenefit" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CurrentStateAndLocalTaxExpenseBenefit" xlink:type="locator" xlink:label="us-gaap_CurrentStateAndLocalTaxExpenseBenefit" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StateAndLocalIncomeTaxExpenseBenefitContinuingOperations" xlink:type="locator" xlink:label="us-gaap_StateAndLocalIncomeTaxExpenseBenefitContinuingOperations" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FederalIncomeTaxExpenseBenefitContinuingOperations" xlink:type="locator" xlink:label="us-gaap_FederalIncomeTaxExpenseBenefitContinuingOperations" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:type="locator" xlink:label="us-gaap_IncomeTaxExpenseBenefit" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_IncomeTaxExpenseBenefit" xlink:to="us-gaap_FederalIncomeTaxExpenseBenefitContinuingOperations" order="10010.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_IncomeTaxExpenseBenefit" xlink:to="us-gaap_StateAndLocalIncomeTaxExpenseBenefitContinuingOperations" order="10020.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_StateAndLocalIncomeTaxExpenseBenefitContinuingOperations" xlink:to="us-gaap_CurrentStateAndLocalTaxExpenseBenefit" order="10030.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_StateAndLocalIncomeTaxExpenseBenefitContinuingOperations" xlink:to="us-gaap_DeferredStateAndLocalIncomeTaxExpenseBenefit" order="10040.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_FederalIncomeTaxExpenseBenefitContinuingOperations" xlink:to="us-gaap_CurrentFederalTaxExpenseBenefit" order="10050.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_FederalIncomeTaxExpenseBenefitContinuingOperations" xlink:to="us-gaap_DeferredFederalIncomeTaxExpenseBenefit" order="10060.00" priority="2" use="optional" weight="1.00" />
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureIncomeTaxesScheduleOfEffectiveIncomeTaxRateDetails" xlink:href="fusb-20201231.xsd#Role_DisclosureIncomeTaxesScheduleOfEffectiveIncomeTaxRateDetails" xlink:type="simple" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureIncomeTaxesScheduleOfEffectiveIncomeTaxRateDetails">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxReconciliationOtherAdjustments" xlink:type="locator" xlink:label="us-gaap_IncomeTaxReconciliationOtherAdjustments" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes" xlink:type="locator" xlink:label="us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes" />
    <link:loc xlink:href="fusb-20201231.xsd#fusb_IncomeTaxReconciliationDeductionsLifeInsuranceAmount" xlink:type="locator" xlink:label="fusb_IncomeTaxReconciliationDeductionsLifeInsuranceAmount" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxReconciliationTaxExemptIncome" xlink:type="locator" xlink:label="us-gaap_IncomeTaxReconciliationTaxExemptIncome" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate" xlink:type="locator" xlink:label="us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:type="locator" xlink:label="us-gaap_IncomeTaxExpenseBenefit" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_IncomeTaxExpenseBenefit" xlink:to="us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate" order="10010.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_IncomeTaxExpenseBenefit" xlink:to="us-gaap_IncomeTaxReconciliationTaxExemptIncome" order="10020.00" priority="2" use="optional" weight="-1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_IncomeTaxExpenseBenefit" xlink:to="fusb_IncomeTaxReconciliationDeductionsLifeInsuranceAmount" order="10030.00" priority="2" use="optional" weight="-1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_IncomeTaxExpenseBenefit" xlink:to="us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes" order="10040.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_IncomeTaxExpenseBenefit" xlink:to="us-gaap_IncomeTaxReconciliationOtherAdjustments" order="10050.00" priority="2" use="optional" weight="1.00" />
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureIncomeTaxesEffectsOfTemporaryDifferencesOfDeferredTaxAssetsAndDeferredTaxLiabilitiesDetails" xlink:href="fusb-20201231.xsd#Role_DisclosureIncomeTaxesEffectsOfTemporaryDifferencesOfDeferredTaxAssetsAndDeferredTaxLiabilitiesDetails" xlink:type="simple" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureIncomeTaxesEffectsOfTemporaryDifferencesOfDeferredTaxAssetsAndDeferredTaxLiabilitiesDetails">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsOther" xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsOther" />
    <link:loc xlink:href="fusb-20201231.xsd#fusb_DeferredTaxAssetsUnrealizedLossesOnDerivativesDesignatedAsCashFlowHedges" xlink:type="locator" xlink:label="fusb_DeferredTaxAssetsUnrealizedLossesOnDerivativesDesignatedAsCashFlowHedges" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsTaxCreditCarryforwards" xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsTaxCreditCarryforwards" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsOperatingLossCarryforwards" xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsOperatingLossCarryforwards" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsDomestic" xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsDomestic" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsImpairmentLosses" xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsImpairmentLosses" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsTaxDeferredExpense" xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsTaxDeferredExpense" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefits" xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefits" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsProvisionForLoanLosses" xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsProvisionForLoanLosses" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxLiabilitiesOther" xlink:type="locator" xlink:label="us-gaap_DeferredTaxLiabilitiesOther" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsUnrealizedLossesOnAvailableforSaleSecuritiesGross" xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsUnrealizedLossesOnAvailableforSaleSecuritiesGross" />
    <link:loc xlink:href="fusb-20201231.xsd#fusb_DeferredTaxLiabilitiesPartnerships" xlink:type="locator" xlink:label="fusb_DeferredTaxLiabilitiesPartnerships" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets" xlink:type="locator" xlink:label="us-gaap_DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxLiabilitiesPropertyPlantAndEquipment" xlink:type="locator" xlink:label="us-gaap_DeferredTaxLiabilitiesPropertyPlantAndEquipment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredIncomeTaxLiabilities" xlink:type="locator" xlink:label="us-gaap_DeferredIncomeTaxLiabilities" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsGross" xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsGross" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsLiabilitiesNet" xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsLiabilitiesNet" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_DeferredTaxAssetsLiabilitiesNet" xlink:to="us-gaap_DeferredTaxAssetsGross" order="10010.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_DeferredTaxAssetsLiabilitiesNet" xlink:to="us-gaap_DeferredIncomeTaxLiabilities" order="10020.00" priority="2" use="optional" weight="-1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_DeferredIncomeTaxLiabilities" xlink:to="us-gaap_DeferredTaxLiabilitiesPropertyPlantAndEquipment" order="10030.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_DeferredIncomeTaxLiabilities" xlink:to="us-gaap_DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets" order="10040.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_DeferredIncomeTaxLiabilities" xlink:to="fusb_DeferredTaxLiabilitiesPartnerships" order="10050.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_DeferredIncomeTaxLiabilities" xlink:to="us-gaap_DeferredTaxAssetsUnrealizedLossesOnAvailableforSaleSecuritiesGross" order="10060.00" priority="2" use="optional" weight="-1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_DeferredIncomeTaxLiabilities" xlink:to="us-gaap_DeferredTaxLiabilitiesOther" order="10070.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_DeferredTaxAssetsGross" xlink:to="us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsProvisionForLoanLosses" order="10080.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_DeferredTaxAssetsGross" xlink:to="us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefits" order="10090.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_DeferredTaxAssetsGross" xlink:to="us-gaap_DeferredTaxAssetsTaxDeferredExpense" order="10100.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_DeferredTaxAssetsGross" xlink:to="us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsImpairmentLosses" order="10110.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_DeferredTaxAssetsGross" xlink:to="us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsDomestic" order="10120.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_DeferredTaxAssetsGross" xlink:to="us-gaap_DeferredTaxAssetsOperatingLossCarryforwards" order="10130.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_DeferredTaxAssetsGross" xlink:to="us-gaap_DeferredTaxAssetsTaxCreditCarryforwards" order="10140.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_DeferredTaxAssetsGross" xlink:to="us-gaap_DeferredTaxAssetsUnrealizedLossesOnAvailableforSaleSecuritiesGross" order="10150.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_DeferredTaxAssetsGross" xlink:to="fusb_DeferredTaxAssetsUnrealizedLossesOnDerivativesDesignatedAsCashFlowHedges" order="10160.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_DeferredTaxAssetsGross" xlink:to="us-gaap_DeferredTaxAssetsOther" order="10170.00" priority="2" use="optional" weight="1.00" />
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureLeasesFutureMinimumOperatingLeasePaymentsDetails" xlink:href="fusb-20201231.xsd#Role_DisclosureLeasesFutureMinimumOperatingLeasePaymentsDetails" xlink:type="simple" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureLeasesFutureMinimumOperatingLeasePaymentsDetails">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterRollingYearFive" xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterRollingYearFive" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFive" xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFive" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFour" xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFour" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearThree" xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearThree" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearTwo" xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearTwo" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextRollingTwelveMonths" xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextRollingTwelveMonths" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextRollingTwelveMonths" order="10010.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearTwo" order="10020.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearThree" order="10030.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFour" order="10040.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFive" order="10050.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterRollingYearFive" order="10060.00" priority="2" use="optional" weight="1.00" />
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureLeasesFutureMinimumOperatingLeasePaymentsDetails2" xlink:href="fusb-20201231.xsd#Role_DisclosureLeasesFutureMinimumOperatingLeasePaymentsDetails2" xlink:type="simple" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureLeasesFutureMinimumOperatingLeasePaymentsDetails2">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiability" xlink:type="locator" xlink:label="us-gaap_OperatingLeaseLiability" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount" xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount" order="10010.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" xlink:to="us-gaap_OperatingLeaseLiability" order="10020.00" priority="2" use="optional" weight="1.00" />
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureSegmentReportingResultsForReportableSegmentsDetails" xlink:href="fusb-20201231.xsd#Role_DisclosureSegmentReportingResultsForReportableSegmentsDetails" xlink:type="simple" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureSegmentReportingResultsForReportableSegmentsDetails">
    <link:loc xlink:href="fusb-20201231.xsd#fusb_ProvisionReductionInReserveForLoanLosses" xlink:type="locator" xlink:label="fusb_ProvisionReductionInReserveForLoanLosses" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestIncomeExpenseNet" xlink:type="locator" xlink:label="us-gaap_InterestIncomeExpenseNet" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss" xlink:type="locator" xlink:label="us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:type="locator" xlink:label="us-gaap_IncomeTaxExpenseBenefit" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:type="locator" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProfitLoss" xlink:type="locator" xlink:label="us-gaap_ProfitLoss" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_ProfitLoss" xlink:to="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" order="10010.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_ProfitLoss" xlink:to="us-gaap_IncomeTaxExpenseBenefit" order="10020.00" priority="2" use="optional" weight="-1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss" xlink:to="us-gaap_InterestIncomeExpenseNet" order="10030.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss" xlink:to="fusb_ProvisionReductionInReserveForLoanLosses" order="10040.00" priority="2" use="optional" weight="-1.00" />
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureOtherOperatingIncomeAndExpenseOtherOperatingIncomeDetails" xlink:href="fusb-20201231.xsd#Role_DisclosureOtherOperatingIncomeAndExpenseOtherOperatingIncomeDetails" xlink:type="simple" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureOtherOperatingIncomeAndExpenseOtherOperatingIncomeDetails">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherIncome" xlink:type="locator" xlink:label="us-gaap_OtherIncome" />
    <link:loc xlink:href="fusb-20201231.xsd#fusb_GainOnSalesOfPremisesAndEquipmentAndOtherAssets" xlink:type="locator" xlink:label="fusb_GainOnSalesOfPremisesAndEquipmentAndOtherAssets" />
    <link:loc xlink:href="fusb-20201231.xsd#fusb_WireTransferFees" xlink:type="locator" xlink:label="fusb_WireTransferFees" />
    <link:loc xlink:href="fusb-20201231.xsd#fusb_OtherIncomeATMFees" xlink:type="locator" xlink:label="fusb_OtherIncomeATMFees" />
    <link:loc xlink:href="fusb-20201231.xsd#fusb_AutoClubRevenue" xlink:type="locator" xlink:label="fusb_AutoClubRevenue" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BankOwnedLifeInsuranceIncome" xlink:type="locator" xlink:label="us-gaap_BankOwnedLifeInsuranceIncome" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NoninterestIncomeOther" xlink:type="locator" xlink:label="us-gaap_NoninterestIncomeOther" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NoninterestIncomeOther" xlink:to="us-gaap_BankOwnedLifeInsuranceIncome" order="10010.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NoninterestIncomeOther" xlink:to="fusb_AutoClubRevenue" order="10020.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NoninterestIncomeOther" xlink:to="fusb_OtherIncomeATMFees" order="10030.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NoninterestIncomeOther" xlink:to="fusb_WireTransferFees" order="10040.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NoninterestIncomeOther" xlink:to="fusb_GainOnSalesOfPremisesAndEquipmentAndOtherAssets" order="10050.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NoninterestIncomeOther" xlink:to="us-gaap_OtherIncome" order="10060.00" priority="2" use="optional" weight="1.00" />
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureOtherOperatingIncomeAndExpenseOtherOperatingExpenseDetails" xlink:href="fusb-20201231.xsd#Role_DisclosureOtherOperatingIncomeAndExpenseOtherOperatingExpenseDetails" xlink:type="simple" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureOtherOperatingIncomeAndExpenseOtherOperatingExpenseDetails">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherCostAndExpenseOperating" xlink:type="locator" xlink:label="us-gaap_OtherCostAndExpenseOperating" />
    <link:loc xlink:href="fusb-20201231.xsd#fusb_ForeclosedRealEstateOtherExpenseNetOfGainOrLossOnSale" xlink:type="locator" xlink:label="fusb_ForeclosedRealEstateOtherExpenseNetOfGainOrLossOnSale" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AmortizationOfIntangibleAssets" xlink:type="locator" xlink:label="us-gaap_AmortizationOfIntangibleAssets" />
    <link:loc xlink:href="fusb-20201231.xsd#fusb_LossOnSalesOfPremisesAndEquipmentAndOtherAssets" xlink:type="locator" xlink:label="fusb_LossOnSalesOfPremisesAndEquipmentAndOtherAssets" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FederalDepositInsuranceCorporationPremiumExpense" xlink:type="locator" xlink:label="us-gaap_FederalDepositInsuranceCorporationPremiumExpense" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GeneralInsuranceExpense" xlink:type="locator" xlink:label="us-gaap_GeneralInsuranceExpense" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CostOfGoodsAndServicesSold" xlink:type="locator" xlink:label="us-gaap_CostOfGoodsAndServicesSold" />
    <link:loc xlink:href="fusb-20201231.xsd#fusb_CollectionAndRecoveries" xlink:type="locator" xlink:label="fusb_CollectionAndRecoveries" />
    <link:loc xlink:href="fusb-20201231.xsd#fusb_BusinessDevelopmentAndTravel" xlink:type="locator" xlink:label="fusb_BusinessDevelopmentAndTravel" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MarketingAndAdvertisingExpense" xlink:type="locator" xlink:label="us-gaap_MarketingAndAdvertisingExpense" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommunicationsAndInformationTechnology" xlink:type="locator" xlink:label="us-gaap_CommunicationsAndInformationTechnology" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SuppliesAndPostageExpense" xlink:type="locator" xlink:label="us-gaap_SuppliesAndPostageExpense" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingExpenses" xlink:type="locator" xlink:label="us-gaap_OperatingExpenses" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_OperatingExpenses" xlink:to="us-gaap_SuppliesAndPostageExpense" order="10010.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_OperatingExpenses" xlink:to="us-gaap_CommunicationsAndInformationTechnology" order="10020.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_OperatingExpenses" xlink:to="us-gaap_MarketingAndAdvertisingExpense" order="10030.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_OperatingExpenses" xlink:to="fusb_BusinessDevelopmentAndTravel" order="10040.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_OperatingExpenses" xlink:to="fusb_CollectionAndRecoveries" order="10050.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_OperatingExpenses" xlink:to="us-gaap_CostOfGoodsAndServicesSold" order="10060.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_OperatingExpenses" xlink:to="us-gaap_GeneralInsuranceExpense" order="10070.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_OperatingExpenses" xlink:to="us-gaap_FederalDepositInsuranceCorporationPremiumExpense" order="10080.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_OperatingExpenses" xlink:to="fusb_LossOnSalesOfPremisesAndEquipmentAndOtherAssets" order="10090.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_OperatingExpenses" xlink:to="us-gaap_AmortizationOfIntangibleAssets" order="10100.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_OperatingExpenses" xlink:to="fusb_ForeclosedRealEstateOtherExpenseNetOfGainOrLossOnSale" order="10110.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_OperatingExpenses" xlink:to="us-gaap_OtherCostAndExpenseOperating" order="10120.00" priority="2" use="optional" weight="1.00" />
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureFirstUSBancsharesIncParentCompanyOnlyFinancialInformationStatementsOfBalanceSheetDetail" xlink:href="fusb-20201231.xsd#Role_DisclosureFirstUSBancsharesIncParentCompanyOnlyFinancialInformationStatementsOfBalanceSheetDetail" xlink:type="simple" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureFirstUSBancsharesIncParentCompanyOnlyFinancialInformationStatementsOfBalanceSheetDetail">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherAssets" xlink:type="locator" xlink:label="us-gaap_OtherAssets" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures" xlink:type="locator" xlink:label="us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:type="locator" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Assets" xlink:type="locator" xlink:label="us-gaap_Assets" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" xlink:type="locator" xlink:label="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherLiabilities" xlink:type="locator" xlink:label="us-gaap_OtherLiabilities" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:type="locator" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_LiabilitiesAndStockholdersEquity" xlink:to="us-gaap_OtherLiabilities" order="10010.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_LiabilitiesAndStockholdersEquity" xlink:to="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" order="10020.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Assets" xlink:to="us-gaap_CashAndCashEquivalentsAtCarryingValue" order="10030.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Assets" xlink:to="us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures" order="10040.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Assets" xlink:to="us-gaap_OtherAssets" order="10050.00" priority="2" use="optional" weight="1.00" />
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureFirstUSBancsharesIncParentCompanyOnlyFinancialInformationStatementsOfOperationsDetail" xlink:href="fusb-20201231.xsd#Role_DisclosureFirstUSBancsharesIncParentCompanyOnlyFinancialInformationStatementsOfOperationsDetail" xlink:type="simple" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureFirstUSBancsharesIncParentCompanyOnlyFinancialInformationStatementsOfOperationsDetail">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingExpenses" xlink:type="locator" xlink:label="us-gaap_OperatingExpenses" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax" xlink:type="locator" xlink:label="us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax" />
    <link:loc xlink:href="fusb-20201231.xsd#fusb_EquityInUndistributedEarningsOfSubsidiary" xlink:type="locator" xlink:label="fusb_EquityInUndistributedEarningsOfSubsidiary" />
    <link:loc xlink:href="fusb-20201231.xsd#fusb_IncomeLossBeforeEquityInUndistributedIncomeOfSubsidiaries" xlink:type="locator" xlink:label="fusb_IncomeLossBeforeEquityInUndistributedIncomeOfSubsidiaries" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProfitLoss" xlink:type="locator" xlink:label="us-gaap_ProfitLoss" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_ProfitLoss" xlink:to="fusb_IncomeLossBeforeEquityInUndistributedIncomeOfSubsidiaries" order="10010.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_ProfitLoss" xlink:to="fusb_EquityInUndistributedEarningsOfSubsidiary" order="10020.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="fusb_IncomeLossBeforeEquityInUndistributedIncomeOfSubsidiaries" xlink:to="us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax" order="10030.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="fusb_IncomeLossBeforeEquityInUndistributedIncomeOfSubsidiaries" xlink:to="us-gaap_OperatingExpenses" order="10040.00" priority="2" use="optional" weight="-1.00" />
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureFirstUSBancsharesIncParentCompanyOnlyFinancialInformationStatementsOfCashFlowDetail" xlink:href="fusb-20201231.xsd#Role_DisclosureFirstUSBancsharesIncParentCompanyOnlyFinancialInformationStatementsOfCashFlowDetail" xlink:type="simple" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureFirstUSBancsharesIncParentCompanyOnlyFinancialInformationStatementsOfCashFlowDetail">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet" xlink:type="locator" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet" />
    <link:loc xlink:href="fusb-20201231.xsd#fusb_DistributionsInExcessOfUndistributedIncomeLossOfSubsidiaries" xlink:type="locator" xlink:label="fusb_DistributionsInExcessOfUndistributedIncomeLossOfSubsidiaries" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProfitLoss" xlink:type="locator" xlink:label="us-gaap_ProfitLoss" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:type="locator" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_ProfitLoss" order="10010.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="fusb_DistributionsInExcessOfUndistributedIncomeLossOfSubsidiaries" order="10020.00" priority="2" use="optional" weight="-1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet" order="10030.00" priority="2" use="optional" weight="-1.00" />
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureQuarterlyDataUnauditedSummaryOfQuarterlyDataDetails" xlink:href="fusb-20201231.xsd#Role_DisclosureQuarterlyDataUnauditedSummaryOfQuarterlyDataDetails" xlink:type="simple" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.firstusbank.com/20201231/taxonomy/role/DisclosureQuarterlyDataUnauditedSummaryOfQuarterlyDataDetails">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NoninterestExpense" xlink:type="locator" xlink:label="us-gaap_NoninterestExpense" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NoninterestIncome" xlink:type="locator" xlink:label="us-gaap_NoninterestIncome" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss" xlink:type="locator" xlink:label="us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:type="locator" xlink:label="us-gaap_IncomeTaxExpenseBenefit" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" xlink:type="locator" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProfitLoss" xlink:type="locator" xlink:label="us-gaap_ProfitLoss" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_ProfitLoss" xlink:to="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" order="10010.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_ProfitLoss" xlink:to="us-gaap_IncomeTaxExpenseBenefit" order="10020.00" priority="2" use="optional" weight="-1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" xlink:to="us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss" order="10030.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" xlink:to="us-gaap_NoninterestIncome" order="10040.00" priority="2" use="optional" weight="1.00" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" xlink:to="us-gaap_NoninterestExpense" order="10050.00" priority="2" use="optional" weight="-1.00" />
  </link:calculationLink>
</link:linkbase>
