As of 2015, the longest-lived American presidents are Gerald Ford, Ronald Reagan and George H. W. Bush. Both Bush, who is third on the list, and Jimmy Carter, who is fourth, are still living and may eventually overtake the other two.
Gerald Ford remains the longest-lived president. He was 93 years old when he passed away in December 2006. He outlived his 1976 Republican rival Ronald Reagan, who died in 2004, by 45 days.
Former president George H. W. Bush is third on the list. If he lives through November 2017, however, he will overtake both Ford and Reagan. Also still living is Jimmy Carter, fourth oldest and 111 days younger than Bush.