X0306 4 2021-11-09 0001701732 Altair Engineering Inc. ALTR 0001839690 Buckner Stephanie C/O ALTAIR ENGINEERING INC. 1820 E. BIG BEAVER RD. TROY MI 48083 1 Chief Operating Officer Class A Common Stock 2022-02-15 4 A 0 2000 0 A 10080 D Class A Common Stock 2022-03-14 4 S 0 81 59.964 D 9999 D Class A Common Stock 2021-11-09 4 A 0 1429 0 A 5264 I By husband Stock Option (Right to Buy) 61.79 2022-02-15 4 A 0 6000 0 A 2032-02-15 Class A Common Stock 6000 6000 D Stock Option (Right to Buy) 80.60 2021-11-09 4 A 0 4280 0 A 2031-11-09 Class A Common Stock 4280 4280 I By husband On February 15, 2022, the Reporting Person was granted 2,000 Class A Common Stock restricted stock units, which vest in 4 equal annual installments commencing February 15, 2023. Includes 5,671 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 $59.96 to $60.27 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 5,437 Class A Common Stock restricted stock units that are unvested. On November 9, 2021, the Reporting Person's husband was granted 1,429 Class A Common Stock restricted stock units, which vest in 4 equal annual installments commencing November 9, 2022. Includes 3,491 Class A Common Stock restricted stock units that are unvested. On February 15, 2022, the Reporting Person was granted 6,000 Class A Common Stock options, the options vest in 4 equal annual installments commencing February 15, 2023. On November 9, 2021, the Reporting Person's husband was granted 4,280 Class A Common Stock options, the options vest in 4 equal annual installments commencing November 9, 2022. /s/ Raoul Maitra, attorney-in-fact for Stephanie Bucker 2022-03-16