To override a presidential veto, a supermajority vote of two-thirds of the voting members of each house, the House of Representatives and the Senate, is required. There are 435 voting representatives in the House. If all these representatives voted, it would take 2/3rds of 435 = 290 votes to override a veto. In the Senate, it also takes a 2/3rds of 100 members = 67 votes to override a veto. (But if only 90 actually voted, then it would take only 2/3 of 90 = 60 votes to override).
Assuming all members turn out to vote, 290 (House) + 67 (Senate) = 357 total votes are required to override a presidential veto.