EXHIBIT 11 AIRGAS, INC. EARNINGS PER SHARE CALCULATIONS Three Months Ended Six Months Ended September 30, September 30, (In thousands, except per share amounts) 1999 1998 1999 1998 Weighted Average Shares Outstanding: Basic shares outstanding 69,700 70,000 69,800 70,100 Stock options - incremental shares 1,300 1,600 1,200 1,600 Contingently issuable shares 200 100 200 100 Diluted shares outstanding 71,200 71,700 71,200 71,800 Net earnings $18,912 $10,480 $27,997 $21,755 Basic earnings per share $ .27 $ .15 $ .40 $ .31 Diluted earnings per share $ .27 $ .15 $ .39 $ .30