<PAGE>
 
                                                                      Exhibit 11


                                 CompUSA Inc.

                                COMPUTATIONS OF
                 INCOME PER COMMON AND COMMON EQUIVALENT SHARE
                     (in thousands, except per share data)

<TABLE> 
<CAPTION> 
                                                          Thirteen Weeks Ended                        Twenty-six Weeks Ended
                                                -------------------------------------        ---------------------------------------
                                                  December 28,          December 23,           December 28,           December 23,
                                                      1996                 1995                    1996                   1995
                                                ---------------      ----------------        ----------------       ----------------

<S>                                              <C>                  <C>                     <C>                    <C> 
Common shares outstanding at     
   beginning of period.......................          90,782               89,336                  90,216                 80,932
Weighted average number of                               
   common shares issued during the                   
   period....................................             385                   43                     604                  4,536
Weighted average treasury shares.............            (379)                 (12)                   (379)                    (4)
Incremental shares related to 
   assumed exercise of stock                 
   options...................................           3,949                3,650                   4,197                  3,580
                                                ---------------      ----------------        ----------------       ----------------


Weighted common and common                                                                                
   equivalent shares.........................          94,737               93,017                  94,638                 89,044
                                                ===============      ================        ================       ================


Net income...................................    $     23,728         $     18,748            $     38,274           $     24,955
                                                ===============      ================        ================       ================


Income per common and common                                                                                
   equivalent share (1)                          $       0.25         $       0.20            $       0.40           $       0.28
                                                ===============      ================        ================       ================

</TABLE> 

---------------------

(1)    The computation of income per common share on a fully diluted basis does
       not materially differ from the amounts calculated on a primary basis
       shown above.