Page 41 Exhibit 11 NATIONAL SERVICE INDUSTRIES, INC. AND SUBSIDIARIES COMPUTATIONS OF NET INCOME PER SHARE OF COMMON STOCK (In thousands, except per-share data) THREE MONTHS ENDED SIX MONTHS ENDED FEB. 29, FEB. 28, FEB. 29, FEB. 28, 1996 1995 1996 1995 Primary: Weighted Average Number of Shares (determined on a monthly basis)..... 48,364 48,859 48,350 49,025 Net Income ........................... $ 19,250 $ 17,578 $ 42,519 $ 38,692 Primary Earnings per Share ........... $ .40 $ .36 $ .88 $ .79 Fully Diluted: Weighted Average Number of Shares Outstanding ........................ 48,364 48,859 48,350 49,025 Additional Shares Assuming Exercise of Options: Options exercised ................ 1,292 982 1,292 982 Treasury stock purchased with proceeds .................. (1,007) (889) (983) (889) Average Common Shares Outstanding (as adjusted) ..................... 48,649 48,952 48,659 49,118 Net Income ........................... $ 19,250 $ 17,578 $ 42,519 $ 38,692 Fully Diluted Earnings per Share ..... $ .40 $ .36 $ .87 $ .79