Humanities › History & Culture The Oldest Presidents in U.S. History Share Flipboard Email Print Getty Images / Getty Images History & Culture American History U.S. Presidents Basics Important Historical Figures Key Events Native American History American Revolution America Moves Westward The Gilded Age Crimes & Disasters The Most Important Inventions of the Industrial Revolution African American History African History Ancient History and Culture Asian History European History Genealogy Inventions Latin American History Medieval & Renaissance History Military History The 20th Century Women's History View More By Jennifer Rosenberg History Expert B.A., History, University of California at Davis Jennifer Rosenberg is a historian and writer who specializes in 20th-century history. our editorial process Jennifer Rosenberg Updated March 18, 2019 Have you ever wondered who was the oldest president in U.S. history? Browse the list below to discover who was the oldest—and youngest—president at the time of their inauguration. U.S. Presidents by Age The U.S. Constitution lists several requirements for presidential eligibility, including that the leader of the United States must be at least 35 years old. Actual presidential ages have varied by as much as several decades. From oldest to youngest, the U.S. presidents were the following ages at the time they were sworn into office: Donald J. Trump (70 years, 7 months, 7 days)Ronald Reagan (69 years, 11 months, 14 days)William H. Harrison (68 years, 0 months, 23 days)James Buchanan (65 years, 10 months, 9 days)George H. W. Bush (64 years, 7 months, 8 days)Zachary Taylor (64 years, 3 months, 8 days)Dwight D. Eisenhower (62 years, 3 months, 6 days)Andrew Jackson (61 years, 11 months, 17 days)John Adams (61 years, 4 months, 4 days)Gerald R. Ford (61 years, 0 months, 26 days)Harry S. Truman (60 years, 11 months, 4 days)James Monroe (58 years, 10 months, 4 days)James Madison (57 years, 11 months, 16 days)Thomas Jefferson (57 years, 10 months, 19 days)John Quincy Adams (57 years, 7 months, 21 days)George Washington (57 years, 2 months, 8 days)Andrew Johnson (56 years, 3 months, 17 days)Woodrow Wilson (56 years, 2 months, 4 days)Richard M. Nixon (56 years, 0 months, 11 days)Benjamin Harrison (55 years, 6 months, 12 days)Warren G. Harding (55 years, 4 months, 2 days)Lyndon B. Johnson (55 years, 2 months, 26 days)Herbert Hoover (54 years, 6 months, 22 days)George W. Bush (54 years, 6 months, 14 days)Rutherford B. Hayes (54 years, 5 months, 0 days)Martin Van Buren (54 years, 2 months, 27 days)William McKinley (54 years, 1 month, 4 days)Jimmy Carter (52 years, 3 months, 19 days)Abraham Lincoln (52 years, 0 months, 20 days)Chester A. Arthur (51 years, 11 months, 14 days)William H. Taft (51 years, 5 months, 17 days)Franklin D. Roosevelt (51 years, 1 month, 4 days)Calvin Coolidge (51 years, 0 months, 29 days)John Tyler (51 years, 0 months, 6 days)Millard Fillmore (50 years, 6 months, 2 days)James K. Polk (49 years, 4 months, 2 days)James A. Garfield (49 years, 3 months, 13 days)Franklin Pierce (48 years, 3 months, 9 days)Grover Cleveland (47 years, 11 months, 14 days)Barack Obama (47 years, 5 months, 16 days)Ulysses S. Grant (46 years, 10 months, 5 days)Bill Clinton (46 years, 5 months, 1 day)John F. Kennedy (43 years, 7 months, 22 days)Theodore Roosevelt (42 years, 10 months, 18 days) * This list contains 44 U.S. presidents rather than 45 because Grover Cleveland, who had two nonsequential terms in office, has only been counted once. Ronald Reagan's Age Though Donald Trump is the oldest person to become president, Ronald Reagan was (so far) the oldest president in office, completing his second term in 1989 a few weeks shy of his 78th birthday. His age was often discussed in the media, particularly during the latter days of his final term, when there was speculation about his mental fitness. (Reagan was officially diagnosed with Alzheimer's disease in 1994, though a few close associates claim that he showed symptoms much earlier.) But was Reagan really that much older than all the other presidents? It depends on how you look at the question. When he entered the White House, 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 ages of these presidents when they 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 Bush left office after serving only a single term. Donald Trump's Age On November 8, 2016, Donald Trump—then 70 years old—became the oldest person to be elected president of the United States. If re-elected in 2020, he will have the chance to surpass Reagan's record and become the country's oldest serving president.