<PAGE>   1



















                                   EXHIBIT 11

                    COMPUTATION OF EARNINGS PER COMMON SHARE



<PAGE>   2


                                                                    EXHIBIT 11
                                                                    PAGE 1 OF 2



                   UNION PLANTERS CORPORATION AND SUBSIDIARIES
                COMPUTATION OF PRIMARY EARNINGS PER COMMON SHARE



<TABLE>
<CAPTION>
                                                         THREE MONTHS ENDED                               NINE MONTHS ENDED
                                                            SEPTEMBER 30,                                  SEPTEMBER  30,
                                                   ----------------------------------          ------------------------------------
                                                       1997                  1996                  1997                    1996
                                                   -----------           ------------          -----------            ------------- 
                                                                    (DOLLARS IN THOUSANDS, EXCEPT PER SHARE DATA)
<S>                                                <C>                   <C>                   <C>                    <C>       
PRIMARY EARNINGS PER COMMON SHARE

Average shares outstanding                          67,010,178             64,006,649             66,278,149             63,389,113
Assumed exercise of options outstanding              1,362,431              1,212,152              1,349,691              1,219,583
                                                  ------------           ------------           ------------           ------------
Primary average shares outstanding                  68,372,609             65,218,801             67,627,840             64,608,696
                                                  ============           ============           ============           ============

Net earnings                                      $     62,435           $     26,612           $    181,480           $    122,388
Less: Preferred stock dividends
        Series B                                            --                     --                     --                    (45)
        Series E                                        (1,125)                (1,743)                (3,834)                (5,239)
                                                  ------------           ------------           ------------           ------------


Net earnings applicable to common shares          $     61,310           $     24,869           $    177,646           $    117,104
                                                  ============           ============           ============           ============


Primary earnings per common share                 $        .90           $        .38           $       2.63           $       1.80
</TABLE>










<PAGE>   3
                                                               EXHIBIT 11
                                                               PAGE 2 OF 2



                   UNION PLANTERS CORPORATION AND SUBSIDIARIES
             COMPUTATION OF FULLY DILUTED EARNINGS PER COMMON SHARE



<TABLE>
<CAPTION>
                                                                   THREE MONTHS ENDED                       NINE MONTHS ENDED 
                                                                     SEPTEMBER 30,                             SEPTEMBER 30    
                                                             ------------------------------           -----------------------------
                                                                1997                 1996                1997               1996 
                                                             ----------           ---------           -----------       -----------
                                                                            (DOLLARS IN THOUSANDS, EXCEPT PER SHARE DATA)
<S>                                                         <C>                  <C>                  <C>               <C>        
FULLY DILUTED EARNINGS PER COMMON SHARE

Average shares outstanding                                   67,010,178           64,006,649           66,278,149        63,389,113
Assumed exercise of options outstanding                       1,458,185            1,460,712            1,444,771         1,320,686
Assumed conversion of preferred stock outstanding:
      Series B                                                       --                   --                   --           148,804
      Series E                                                2,994,970            4,355,961            3,451,489         4,363,825
                                                            -----------          -----------          -----------       -----------

Fully diluted average shares outstanding                     71,463,333           69,823,322           71,174,409        69,222,428
                                                            ===========          ===========          ===========       ===========


Net earnings                                                $    62,435          $    26,612          $   181,480       $   122,388
Less: Preferred stock dividends                                      --                   --                   --                --
                                                            -----------          -----------          -----------       -----------


Net earnings applicable to common shares                    $    62,435          $    26,612          $   181,480       $   122,388
                                                            ===========          ===========          ===========       ===========


Fully diluted earnings per common share                     $       .87          $       .38          $      2.55       $      1.76
</TABLE>