Who Was the Oldest President of the United States?

Who do you think is the oldest president in United States history? Up until recently, the oldest president in office was Ronald Reagan, but the oldest to become president was Donald Trump. Trump has Reagan beat by nearly 8 months, entering office at the age of 70 years, 220 days. Reagan took his first oath of office at the age of 69 years, 349 days.

Both of those benchmarks were surpassed as of the 2020 election, however. When Joe Biden took office on Jan. 20, 2021, he became the oldest president both to enter office and to be in office. His age on Inaguration Day was be 78 years, 61 days; for comparison, Reagan left office at the age of 77 years, 349 days.

Perspective on Presidential Age

Few Americans who were adults during the Reagan administration can forget how much the President's age was discussed in the media, particularly during the latter years of his second term in office. But was Reagan really that much older than all the other presidents? It depends on how you look at the question. When he entered office, Reagan was less than two years older than William Henry Harrison, four years older than James Buchanan, and five years older than George H.W. Bush, who succeeded Reagan as President. However, the gaps grow wider when you look at the respective ages when these presidents left office. Reagan was a two-term president and left office at the age of 77. Harrison served only 1 month in office, and both Buchanan and and Bush served only a single full term.

All the Presidents' Ages 

Here are the ages of all of the U.S. presidents at the time of their inauguration, listed from oldest to youngest. Grover Cleveland, who served two non-sequential terms, is listed only once.  

1. Joe Biden (78 years, 2 months, 0 days)
2. Donald Trump (70 years, 7 months, 7 days)
3. Ronald Reagan (69 years, 11 months, 14 days)
4. William H. Harrison (68 years, 0 months, 23 days)
5. James Buchanan (65 years, 10 months, 9 days)
6. George H. W. Bush (64 years, 7 months, 8 days)
7. Zachary Taylor (64 years, 3 months, 8 days)
8. Dwight D. Eisenhower (62 years, 3 months, 6 days)
9. Andrew Jackson (61 years, 11 months, 17 days)
10. John Adams (61 years, 4 months, 4 days)
11. Gerald R. Ford (61 years, 0 months, 26 days)
12. Harry S. Truman (60 years, 11 months, 4 days)
13. James Monroe (58 years 10 months, 4 days)
14. James Madison (57 years, 11 months, 16 days)
15. Thomas Jefferson (57 years, 10 months, 19 days)
16. John Quincy Adams (57 years, 7 months, 21 days)
17. George Washington (57 years, 2 months, 8 days)
18. Andrew Johnson (56 years, 3 months, 17 days)
19. Woodrow Wilson (56 years, 2 months, 4 days)
20. Richard M. Nixon (56 years, 0 months, 11 days)
21. Benjamin Harrison (55 years, 6 months, 12 days)
22. Warren G. Harding (55 years, 4 months, 2 days)
23. Lyndon B. Johnson (55 years, 2 months, 26 days)
24. Herbert Hoover (54 years, 6 months, 22 days)
25. George W. Bush (54 years, 6 months, 14 days)
26. Rutherford B. Hayes (54 years, 5 months, 0 days)
27. Martin Van Buren (54 years, 2 months, 27 days)
28. William McKinley (54 years, 1 month, 4 days)
29. Jimmy Carter (52 years, 3 months, 19 days)
30. Abraham Lincoln (52 years, 0 months, 20 days)
31. Chester A. Arthur (51 years, 11 months, 14 days)
32. William H. Taft (51 years, 5 months, 17 days)
33. Franklin D. Roosevelt (51 years, 1 month, 4 days)
34. Calvin Coolidge (51 years, 0 months, 29 days)
35. John Tyler (51 years, 0 months, 6 days)
36. Millard Fillmore (50 years, 6 months, 2 days)
37. James K. Polk (49 years, 4 months, 2 days)
38. James A. Garfield (49 years, 3 months, 13 days)
39. Franklin Pierce (48 years, 3 months, 9 days)
40. Grover Cleveland (47 years, 11 months, 14 days)
41. Barack Obama (47 years, 5 months, 16 days)
42. Ulysses S. Grant (46 years, 10 months, 5 days)
43. Bill Clinton (46 years, 5 months, 1 day)
44. John F. Kennedy (43 years, 7 months, 22 days)
45. Theodore Roosevelt (42 years, 10 months, 18 days)