Let’s be real for a second: the idea of a US presidents ranking by IQ is kind of a mess. People love lists. We love to know who the "smartest" guy in the room was, especially when that room is the Oval Office. But here’s the kicker—the modern IQ test didn’t even exist when most of these men were alive. Alfred Binet didn’t develop the precursor to the modern test until 1905.
So, how do we get these numbers?
Mostly, it comes down to a field called historiometry. Specifically, a massive study by UC Davis psychologist Dean Keith Simonton in 2006. He didn't just guess; he used biographical data, records of intellectual "brilliance," and personality traits to estimate where these leaders would fall on the scale.
The High-Flyers: Who Topped the List?
If you’re looking for the absolute peak of the US presidents ranking by IQ, you have to look at John Quincy Adams.
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Honestly, the guy was a walking encyclopedia. Most estimates put his IQ somewhere around 175. To give you some perspective, a "genius" level is usually considered anything over 140. Adams was reading Greek and Latin by the time most kids were learning to tie their shoes. He was a Harvard grad, a linguist, and basically a professional intellectual who happened to stumble into the presidency.
Then you have Thomas Jefferson.
He usually sits at number two with an estimated IQ of 160. Jefferson wasn’t just a politician; he was an architect, a musician, a scientist, and a tinkerer. He literally founded the University of Virginia. When JFK hosted a dinner for Nobel Prize winners in 1962, he famously said it was the most extraordinary collection of talent the White House had seen—except for when Jefferson dined alone.
It’s a great line. It also happens to be true.
The Ivy League Intellectuals
- James Madison (160): The "Father of the Constitution" was a Princeton man who basically drafted the blueprint for American government. He was tiny in stature but a heavyweight in pure logic.
- John F. Kennedy (159.8): This one often surprises people because JFK had a bit of a "playboy" reputation, but his intellectual depth was massive. He was a Harvard grad and a Pulitzer Prize winner.
- Bill Clinton (159): Whatever you think of his politics, the man was a Rhodes Scholar. He was known for having a "photographic" memory and could speak extemporaneously on policy for hours without notes.
Does a High IQ Equal a Great Presidency?
Short answer: Not really.
This is where the US presidents ranking by IQ starts to get tricky. If IQ were the only metric for success, John Quincy Adams would be the greatest president in history. He isn't. Most historians rank him as "average" or even "below average" as a leader. He was too smart for his own good, often struggling to relate to the average voter or play the "game" of politics.
On the flip side, look at George Washington.
His estimated IQ is around 132. That's still very high—top 2% of the population—but it’s nowhere near Jefferson or Adams. Yet, Washington is almost always ranked in the top three "greatest" presidents. He had something the high-IQ guys sometimes lacked: judgment and emotional intelligence.
The "Bottom" of the List
It’s a bit of a misnomer to talk about the "dumbest" presidents. Even the men at the bottom of the US presidents ranking by IQ are usually well above the national average.
- Ulysses S. Grant (130): Often unfairly maligned because of the scandals in his administration. In reality, he was a brilliant military strategist.
- Warren G. Harding (124): Usually cited as the lowest on the list. He was a "newspaper man" who admitted he wasn't fit for the office.
- George W. Bush (138.5): This is a controversial one. While a 2006 study placed him on the lower end relative to other presidents, his score of 138 is still higher than the vast majority of the public.
The Trouble with Estimates
We have to acknowledge the limitations here. Simonton's study is brilliant, but it’s still an estimate. It relies on "Openness to Experience" as a proxy for intelligence.
If a president wrote a lot of books or traveled the world, they got a higher score. If they were more "man of the people" types like Andrew Jackson, their "intellectual" score might suffer even if they were incredibly "street smart" or cunning.
For instance, Abraham Lincoln is estimated at 150. He had almost no formal schooling. He taught himself law. He read the Bible and Shakespeare by candlelight. How do you quantify that kind of grit? You can’t, really.
What This Means for Us Today
When we look at a US presidents ranking by IQ, we’re usually looking for reassurance. We want to believe the person in charge is "smarter" than us. But history shows that "brilliance" can be a double-edged sword.
The most successful presidents weren't always the ones with the highest test scores. They were the ones who could communicate a vision, manage a cabinet of "rivals," and make tough calls when the data was messy.
If you want to dive deeper into this, don't just look at the numbers. Read the actual writings of these men. Read the Federalist Papers by Madison or the Memoirs of Ulysses S. Grant. The "quality" of their thought is usually much more telling than a theoretical number from a 2006 psychology paper.
Actionable Takeaways for History Buffs
- Ignore the Hoaxes: You’ll often see "viral" lists on social media claiming certain modern presidents have IQs of 180 or 80. These are almost always fake. Stick to peer-reviewed studies like Simonton's.
- Context is King: A high IQ in 1800 meant something different than it does in 2026. Education was less standardized, and "intelligence" was often measured by classical knowledge.
- Look for "Executive Function": If you're studying leadership, look at how presidents processed information. The ability to synthesize complex data (like Bill Clinton or Barack Obama) is often more important than raw IQ.
The takeaway? Being a genius is great, but in the White House, being a leader is better.
Next Steps for Your Research
- Compare the Rankings: Cross-reference Simonton's IQ estimates with the C-SPAN "Presidential Historian Survey" to see the disconnect between intelligence and "greatness."
- Read Primary Sources: Pick a high-IQ president (like J.Q. Adams) and a lower-IQ one (like Harry Truman) and read their diaries. The difference in their thinking styles is fascinating.
- Investigate Historiometry: Look into the methodology of "distance assessment" to understand how psychologists study historical figures without meeting them.