<SEC-DOCUMENT>0001039399-18-000042.txt : 20180522
<SEC-HEADER>0001039399-18-000042.hdr.sgml : 20180522
<ACCEPTANCE-DATETIME>20180522183835
ACCESSION NUMBER:		0001039399-18-000042
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20180518
FILED AS OF DATE:		20180522
DATE AS OF CHANGE:		20180522

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			MAIER LOTHAR
		CENTRAL INDEX KEY:			0001253573

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-50307
		FILM NUMBER:		18853566

	MAIL ADDRESS:	
		STREET 1:		1630 MCCARTHY BLVD
		CITY:			MILPITAS
		STATE:			CA
		ZIP:			95035

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			FORMFACTOR INC
		CENTRAL INDEX KEY:			0001039399
		STANDARD INDUSTRIAL CLASSIFICATION:	SEMICONDUCTORS & RELATED DEVICES [3674]
		IRS NUMBER:				133711155
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1226

	BUSINESS ADDRESS:	
		STREET 1:		7005 SOUTHFRONT ROAD
		CITY:			LIVERMORE
		STATE:			CA
		ZIP:			94551
		BUSINESS PHONE:		9252433522

	MAIL ADDRESS:	
		STREET 1:		7005 SOUTHFRONT ROAD
		CITY:			LIVERMORE
		STATE:			CA
		ZIP:			94551
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_152702870188990.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-05-18</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001039399</issuerCik>
        <issuerName>FORMFACTOR INC</issuerName>
        <issuerTradingSymbol>FORM</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001253573</rptOwnerCik>
            <rptOwnerName>MAIER LOTHAR</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>7005 SOUTHFRONT ROAD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>LIVERMORE</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94551</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Restricted Stock Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0.0</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2018-05-18</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>9000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F2"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>9000.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>9000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Restricted Stock Units Vest and become exercisable in 12 equal monthly installments with the vesting dates beginning on June 18, 2018 and ending on May 18, 2019. Settlements of vested units into common stock will occur on the earlier of May 18, 2019 or the date the reporting person ceases to provide service to the Issuer, and thereafter on the first market trading day if the applicable date is not a market trading day.</footnote>
        <footnote id="F2">If the reporting person ceases to provide services to the Issuer for any reason, all Restricted Stock Units that have not yet vested shall be forfeited without consideration except as provided in our Equity Grant Policy for Outside Directors and any other agreements between the reporting person and Issuer, regarding award vesting and exercisability.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>By: Jason Cohen, Attorney-in-Fact For: Lothar Maier</signatureName>
        <signatureDate>2018-05-22</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
