<PAGE>
 
                                                                    EXHIBIT 11.1

                        WORKGROUP TECHNOLOGY CORPORATION
                     COMPUTATION OF WEIGHTED AVERAGE SHARES
                   USED IN COMPUTING INCOME PER SHARE AMOUNTS

<TABLE>
<CAPTION>
 
 
                                                    Primary        Fully
Type of Security                                     Shares       Diluted
----------------                                   ----------    ----------
<S>                                          <C>              <C>
For the three months ended September
 30, 1996:
    Common Stock, beginning of period              7,948,000    7,948,000
    Weighted average common stock        
     issued during the period                         17,000       17,000  
    Common stock equivalents                               -            -
    Treasury stock buyback                                 -            -
                                                   ---------    ---------
 
       Weighted average shares of
        common stock outstanding                   7,965,000    7,965,000
                                                   =========    =========
       Net loss per share                         $    (0.10)  $    (0.10)
                                                  ==========    =========
 
For the three months ended September
 30, 1995:
    Common Stock, beginning of period              1,724,000    1,724,000
    Cheap stock outstanding during the 
     period                                        1,370,000    1,370,000
    Weighted average common stock         
     issued during the period                              -            -
    Common stock equivalents                       3,359,000    3,359,000
    Treasury stock buyback                          (249,000)    (249,000)
                                                  -----------  -----------
       Weighted average shares of                  
        common stock outstanding                   6,204,000    6,204,000
                                                 ============  ===========
       Net income per share                       $     0.06   $     0.06
                                                 ============  ===========                                        
For the six months ended September 30,
 1996:
    Common Stock, beginning of period              7,926,000    7,926,000
    Weighted average common stock                    
     issued during the period                         23,000       23,000
    Common stock equivalents                       1,391,000    1,388,000
    Treasury stock buyback                          (211,000)    (210,000)
                                                  -----------  -----------
       Weighted average shares of                  
        common stock outstanding                   9,129,000    9,127,000
                                                 ============  ===========
       Net income per share                       $     0.01   $     0.01
                                                 ============  ===========
 
For the six months ended September 30,
 1995:
    Common Stock, beginning of period              1,722,000    1,722,000
    Cheap stock outstanding during the             
     period                                        1,370,000    1,370,000
    Weighted average common stock                     
     issued during the period                          2,000        2,000
    Common stock equivalents                       3,364,000    3,364,000
    Treasury stock buyback                          (249,000)    (249,000)
                                                  -----------  -----------
       Weighted average shares of                
        common stock outstanding                    6,209,000    6,209,000
                                                 ============  ===========
       Net income per share                        $     0.09   $     0.09
                                                 ============  ===========
 
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(1)  All common share amounts have been restated to reflect a 3-into-2 reverse
     stock split.
(2)  In accordance with the Securities and Exchange Commission, issuances of
     common stock and common stock equivalents, within one year prior to the
     initial filing of the registration statement, at share prices below the
     assumed initial public offering price of $14.50 per share (cheap stock),
     are considered to have been made in anticipation of the contemplated public
     offering for which this registration statement was prepared. Accordingly,
     these stock issuances are treated as if issued and outstanding, using the
     treasury stock method, since the inception of the Company. See Note 4 of
     Notes to the Consolidated Financial Statements.

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