X0306 4 2020-08-06 0 0001701732 Altair Engineering Inc. ALTR 0001720686 Chouinard Brett R C/O ALTAIR ENGINEERING INC. 1820 E. BIG BEAVER ROAD TROY MI 48083 1 1 0 0 See Remarks Class A Common Stock 2020-08-06 4 S 0 1500 41.607 D 50569 D Class A Common Stock 2020-08-06 4 S 0 1500 41.753 D 49069 D The sale of the shares of Class A Common Stock were made pursuant to a plan intended to comply with Rule 10b5-1 of the Exchange Act, previously entered into on May 22, 2020. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $40.72 to $41.715 per share, inclusive. The reporting person undertakes to provide to Altair Engineering Inc., any security holder of Altair Engineering Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth herein. Includes 11,136 Class A Common Stock restricted stock units that are unvested. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $41.72 to $41.93 per share, inclusive. The reporting person undertakes to provide to Altair Engineering Inc., any security holder of Altair Engineering Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth herein. President & Chief Operating Officer /s/ Raoul Maitra, attorney-in-fact for Brett R. Chouinard 2020-08-07