How old do citizens have to be to vote for President?

1. The Constitution sets the voting age through one of its amendments. 2. Citizens eighteen and older can vote for President. 3. The same age also marks when men must register for the Selective Service. 4. Sixteen is too young, because no amendment lowers the voting age below eighteen. _Source: USCIS Civics Flash Cards M-623 (rev. 02/12), public domain, official civics question 54_