<PAGE>

                                  EXHIBIT 11

                   ACT MANUFACTURING, INC. AND SUBSIDIARIES

                  Computation of Net Income Per Common Share

                   THREE MONTHS ENDED JUNE 30, 2000 AND 1999
                     (in thousands, except per share data)
                                  (unaudited)

<TABLE>
<CAPTION>
                                                                                          Three Months Ended June 30,
                                                                                         ---------------------------

                                                                                             2000            1999
                                                                                             ----            ----
<S>                                                                                         <C>             <C>
BASIC NET INCOME PER COMMON SHARE:
   Net income as reported.......................................................            $ 7,028         $ 1,028
   Weighted average number of common shares outstanding:
      Common stock..............................................................             16,716          12,931
                                                                                            -------         -------

      Basic net income per common share.........................................            $  0.42         $  0.08
                                                                                            =======         =======

DILUTED NET INCOME PER COMMON SHARE:
   Net income as reported.......................................................            $ 7,028         $ 1,028
   Weighted average number of shares outstanding:
      Common stock..............................................................             16,716          12,931
      Effect of stock options...................................................              1,029             388
                                                                                            -------         -------

         Total..................................................................             17,745          13,319
                                                                                            -------         -------

      Diluted net income per common share.......................................            $  0.40         $  0.08
                                                                                            =======         =======
</TABLE>
                    SIX MONTHS ENDED JUNE 30, 2000 AND 1999
                     (in thousands except per share data)
                                  (unaudited)


<TABLE>
<CAPTION>
                                                                                          Six Months Ended June 30,
                                                                                          ------------------------
                                                                                           2000              1999
                                                                                           ----              ----
<S>                                                                                         <C>             <C>
BASIC NET INCOME PER COMMON SHARE:
   Net income as reported.......................................................            $13,178         $ 2,878
   Weighted average number of common shares outstanding:
      Common stock..............................................................             16,631          12,898
                                                                                            -------         -------

      Basic net income per common share.........................................            $  0.79         $  0.22
                                                                                            =======         =======

DILUTED NET INCOME PER COMMON SHARE:
   Net income as reported.......................................................            $13,178         $ 2,878
   Weighted average number of shares outstanding:
      Common stock..............................................................             16,631          12,898
      Effect of stock options...................................................              1,124             427
                                                                                            -------         -------

         Total..................................................................             17,755          13,325
                                                                                            -------         -------

      Diluted net income per common share.......................................            $  0.74         $  0.22
                                                                                            =======         =======
</TABLE>