
<PAGE>
 
                    SEI INVESTMENTS COMPANY AND SUBSIDIARIES
                    ----------------------------------------

                  EXHIBIT 11 - EARNINGS PER SHARE CALCULATION
                  -------------------------------------------

                   FOR THE THREE-MONTH PERIOD ENDED MARCH 31,
                   ------------------------------------------


<TABLE>
<CAPTION>
 
 
                                         1997                 1996    
                                      -----------          -----------
<S>                                   <C>                  <C>        
                                                                      
Earnings per common and common                                        
  equivalent share (Primary EPS):                                     
                                                                      
  Net income                          $ 4,801,000          $ 5,793,000
                                      -----------          -----------
                                                                      
  Weighted average number of                                          
  shares issued and outstanding        18,532,000           18,509,000
                                                                      
  Dilutive effect (excess of                                          
  number of shares issuable over                                      
  number of shares assumed to be                                      
  repurchased with the proceeds,                                      
  using the average market price                                      
  during the period) of                                               
  outstanding options                     730,000              973,000
                                      -----------          -----------
                                                                      
  Adjusted weighted average number                                    
  of shares outstanding                19,262,000           19,482,000
                                      -----------          -----------
                                                                      
  Earnings per common and common                                      
  equivalent share                    $       .25          $       .30
                                      -----------          ----------- 
 
</TABLE>

                                       17

<PAGE>
 
                    SEI INVESTMENTS COMPANY AND SUBSIDIARIES
                    ----------------------------------------

                  EXHIBIT 11 - EARNINGS PER SHARE CALCULATION
                  -------------------------------------------

                   FOR THE THREE-MONTH PERIOD ENDED MARCH 31,
                   ------------------------------------------


<TABLE>
<CAPTION>
 
 
                                                      1997            1996    
                                                   -----------     -----------
<S>                                                <C>             <C>        
                                                                              
Earnings per common and common                                                
  equivalent share, assuming full dilution                                    
  (Fully diluted EPS):                                                        
                                                                              
  Net income                                       $ 4,801,000     $ 5,793,000
                                                   -----------     -----------
                                                                              
  Weighted average number of                                                  
  shares issued and outstanding                     18,532,000      18,509,000
                                                                              
  Dilutive effect (excess of                                                  
  number of shares issuable over                                              
  number of shares assumed to be                                              
  repurchased with the proceeds,                                              
  using the higher of the average market price                                
  or ending price during the period) of                                       
  outstanding options                                  730,000         973,000
                                                   -----------     -----------
                                                                              
  Adjusted weighted average number                                            
  of shares outstanding, assuming full dilution     19,262,000      19,482,000
                                                   -----------     -----------
                                                                              
  Earnings per common and common                                              
  equivalent share, assuming full dilution         $       .25     $       .30
                                                   -----------     ----------- 
 
</TABLE>

                                       18

