EXHIBIT 11 AIRGAS, INC. EARNINGS PER SHARE CALCULATIONS Three Months Ended Nine Months Ended December 31, December 31, (In thousands, except per share amounts) 1999 1998 1999 1998 Weighted Average Shares Outstanding: Basic shares outstanding 69,200 69,700 69,600 70,000 Stock options - incremental shares 1,000 1,300 1,100 1,500 Contingently issuable shares 600 600 300 200 Diluted shares outstanding 70,800 71,600 71,000 71,700 Net earnings $ 9,760 $22,088 $37,757 $43,843 Basic earnings per share $ .14 $ .32 $ .54 $ .63 Diluted earnings per share $ .14 $ .31 $ .53 $ .61