How smart are U.S. presidents?
In a 2006 study, UC Davis professor Dean Simonton used historiometric methods to estimate each president’s IQ. Simonton analyzed information from each president’s biographies, speeches and writings that would indicate intelligence.
Simonton estimated four different IQ values for each president. At InsideGov, we averaged all four IQs to get our rankings of the 15 least intelligent presidents in U.S. history. Note that President Obama was not included in the study.
With an average IQ of 126.4, these presidents are still smart, but the bar is set pretty high by the most intelligent commanders-in-chief. For reference, the average IQ for the general public is 100.
This list is by no means definitive, but it should give a general overview of each president’s relative intelligence.
Key Takeaways
- A 2006 study estimated the IQs of U.S. Presidents, placing Ulysses S. Grant with the lowest at 120, and John Quincy Adams as the highest at 168.75.
- Despite lower IQs, presidents like Ronald Reagan have been ranked highly effective by Americans.
- Intelligence doesn’t strictly correlate with presidential success, as seen in varying approval ratings across presidents with different IQ scores.
- The study suggests that while intelligence is a factor, it’s not the sole determinant of a president’s effectiveness and legacy.
Let’s explore the president with the lowest IQ in U.S. History:
- Ulysses S. Grant: IQ 120
- James Monroe: IQ 124.13
- Warren G. Harding: IQ 124.3
- George W. Bush: IQ 124.88
- Andrew Johnson: IQ 125.65
- Zachary Taylor: IQ 125.65
- James Buchanan: IQ 125.93
- Andrew Jackson: IQ 126.25
- William Howard Taft: IQ 126.9
- Gerald Ford: IQ 127.08
- Calvin Coolidge: IQ 127.1
- Harry Truman: IQ 127.55
- Lyndon B. Johnson: IQ 127.83
- Herbert Hoover: IQ 129.78
- Ronald Reagan: IQ 130
#15. Ronald Reagan
Estimated IQ: 130
College: Eureka College
Although Reagan ranks lower than most presidents in terms of IQ, he is considered to be one of the most effective presidents. In fact, in a 2013 Gallup poll, Americans ranked Reagan as the second best modern U.S. president.
#14. Herbert Hoover
Estimated IQ: 129.78
College: Stanford University
Hoover was part of the first class to enter Stanford University. Although he had a successful career as a mining engineer, Hoover struggled to deal with the onset of the Great Depression as president.
#13. Lyndon B. Johnson
Estimated IQ: 127.83
College: Southwest Texas State Teachers College
Before entering politics, LBJ excelled as a teacher at an impoverished school. As president, Johnson pushed an aggressive reform agenda and navigated the beginning of the Vietnam War.
#12. Harry Truman
Estimated IQ: 127.55
College: Spalding’s Commercial College (did not graduate)
Truman entered the White House with one of the highest presidential approval ratings in history, but soon lost public support. He also had one of the most interesting jobs before becoming president, working at a men’s haberdashery store.
#11. Calvin Coolidge
Estimated IQ: 127.1
College: Amherst College
Known as “Silent Cal,” President Coolidge was a notoriously taciturn president. Although the end of his presidency was marred by economic collapse in the U.S., he is still admired by conservatives today for his belief in a small central government.
#10. Gerald Ford
Estimated IQ: 127.08
College: University of Michigan
A football star at the University of Michigan, Ford received contract offers from the Green Bay Packers and Detroit Lions. Instead, he opted for a different career path, enrolling at Yale Law School.
#9. William Howard Taft
Estimated IQ: 126.9
College: Yale University
When Teddy Roosevelt hand-picked Taft as his successor, he was expecting someone who would push an active reform agenda. However, Taft proved to a more hesitant leader, even writing to Roosevelt, “I do not know if I have had harder luck than other presidents, but I do know that I have succeeded far less than others.”
#8. Andrew Jackson
Estimated IQ: 126.25
College: None
Andrew Jackson had a fearsome reputation as a politician and soldier. He was known to duel his rivals—even to the death—and was a quick-tempered leader. His presidency involved several controversial events such as the Trail of Tears and his attempts to destroy the Federal Bank.
#7. James Buchanan
Estimated IQ: 125.93
College: Dickinson College
Buchanan is often considered to be one of the worst presidents in history for his failure to deal with the issue of slavery. In fact, Buchanan ranked dead-last among U.S. presidents in a 2015 poll conducted by the Brookings Institute.
#6. Zachary Taylor
Estimated IQ: 125.65
College: None
Nicknamed “Old Rough and Ready,” Zachary Taylor was a celebrated war hero for his role in the Mexican-American War. Unfortunately, his military skills didn’t translate into a successful presidency.
#5. Andrew Johnson
Estimated IQ: 125.65
College: None
Johnson was born in a log cabin to a family of modest means. Like Taylor, Johnson never received a formal college education, but had a knack for climbing the political ladder.
#4. George W. Bush
Estimated IQ: 124.88
College: Yale University
Throughout Bush’s presidency, the media frequently raised questions about his intelligence, often pointing to his verbal slips. New York Magazine’s Jonathan Chait even wrote: “I see only evidence of a man who not only lacks the ability to think analytically but disdains the very notion of it.”
While it’s true that Bush ranks among the least intelligent presidents, his estimated IQ places him around the average score for a college graduate in the United States.
#3. Warren G. Harding
Estimated IQ: 124.3
College: Ohio Central College
Harding had a diverse career before entering politics, working as a teacher, insurance salesman and journalist. Harding’s tenure as president was abruptly cut short, when he suffered a fatal heart attack during his third year in office.
#2. James Monroe
Estimated IQ: 124.13
College: The College of William and Mary (did not graduate)
Besides George Washington, Monroe was the only president to run unopposed for re-election. Although he may have lacked the intellectual brilliance of some of the other founding fathers, Monroe was nonetheless a successful president.
#1. Ulysses S. Grant
Estimated IQ: 120
College: United States Military Academy
Unlike his rival, Robert E. Lee, Grant was an average student at West Point. While there’s no doubting Grant’s contribution to ending the Civil War, he was a lackluster president. Historians have noted his rough style of conversation and tendency to binge drink.
Overview of the 15 Least Intelligent Presidents
Note: presidents are ordered from most to least recent.
Overview of the 15 Most Intelligent Presidents
Note: presidents are ordered from most to least recent.
Total List
1. John Quincy Adams: 168.75
2. Thomas Jefferson: 153.75
3. John F. Kennedy: 150.65
4. Bill Clinton: 148.8
5. Woodrow Wilson: 145.1
6. Jimmy Carter: 145.1
7. John Adams: 142.5
8. Theodore Roosevelt: 142.28
9. James Garfield: 141.5
10. Chester Arthur: 141.5
11. James Madison: 141.25
12. Franklin D. Roosevelt: 139.63
13. John Tyler: 136.2
14. Millard Fillmore: 135.98
15. Franklin Pierce: 134.78
16. William Henry Harrison: 133.93
17. Rutherford B. Hayes: 133.93
18. Martin Van Buren: 133.35
19. George Washington: 132.5
20. Benjamin Harrison: 132.15
21. Dwight D. Eisenhower: 131.9
22. Richard Nixon: 131
23. Grover Cleveland: 130.95
24. James K. Polk: 130.2
25. William McKinley: 130.18
26. George H. W. Bush: 130.13
27. Ronald Reagan: 130
28. Herbert Hoover: 129.78
29. Lyndon B. Johnson: 127.83
30. Harry Truman: 127.55
31. Calvin Coolidge: 127.1
32. Gerald Ford: 127.08
33. William Howard Taft: 126.9
34. Andrew Jackson: 126.25
35. James Buchanan: 125.93
36. Zachary Taylor: 125.65
37. Andrew Johnson: 127.83
38. George W. Bush: 124.88
39. Warren G. Harding: 124.3
40. James Monroe: 124.13
41. Ulysses S. Grant: 120
Approval Ratings—Least Intelligent
Does having a high IQ translate to a successful presidency? We looked at the approval ratings of the three least intelligent and most intelligent modern U.S. presidents.
Below are the approval ratings for the three least intelligent modern U.S. presidents:
Bush Average Approval Rating: 47.48%
Ford Average Approval Rating: 45.78%
Truman Average Approval Rating: 42.6%
Approval Ratings—Most Intelligent
Below are the approval ratings for the three most intelligent modern U.S. presidents:
Kennedy Average Approval Rating: 70.53%
Clinton Average Approval Rating: 54.8%
Carter Average Approval Rating: 45.78%