Exhibit 11 AIRGAS, INC. AND SUBSIDIARIES EARNINGS PER SHARE CALCULATIONS For the Years Ended March 31, 1999, 1998 and 1997 Years Ended March 31, 1999 1998 1997 Weighted Average Shares Outstanding: Basic shares outstanding 70,000,000 68,700,000 65,900,000 Net common stock equivalents 1,700,000 2,100,000 2,700,000 Diluted shares outstanding 71,700,000 70,800,000 68,600,000 Net earnings $51,924,000 $40,540,000 $23,266,000 Basic earnings per share $ .74 $ .59 $ .35 Diluted earnings per share $ .72 $ .57 $ .34