X0306 4 2021-03-04 0 0001701732 Altair Engineering Inc. ALTR 0001720642 Dias Nelson C/O ALTAIR ENGINEERING INC. 1820 E. BIG BEAVER ROAD TROY MI 48083 0 1 0 0 Chief Revenue Officer Class A Common Stock 2021-03-04 4 S 0 105 61.509 D 25421 D The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $61.415 to $61.51 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 3,322 Class A Common Stock restricted stock units that are unvested. /s/ Raoul Maitra, attorney-in-fact for Nelson Navin Patrick Dias 2021-03-08