Search for the highest IQ ever recorded and you will find a confident list: 228, 250, even 300. The names repeat from article to article, usually with a breathless line about genius beyond measure.
The problem is that most of those numbers were never measured in any meaningful sense, and some could not be measured at all. Once you understand how modern IQ scores work, the famous claims start to wobble. Here is where they came from, why they don't add up, and what the real ceiling looks like.
The usual names on the list
A few people appear on almost every "highest IQ" list:
- William James Sidis, a child prodigy in early 20th-century America, often credited with an IQ of 250 to 300.
- Marilyn vos Savant, an American columnist once listed by Guinness World Records with an IQ of 228.
- Terence Tao, the mathematician, who showed extraordinary ability as a young child and is often given a very high figure online.
- Historical figures such as Goethe, Leonardo da Vinci or Isaac Newton, assigned scores of 190 or more.
Each case has a different problem, but they share one thing: the headline number is far shakier than it looks.
Why the famous numbers don't hold up
Sidis: a number nobody measured
Sidis was clearly exceptional. He entered Harvard as a young boy and was reported to read and learn languages at a remarkable pace. But there is no reliable record of him taking a standardised IQ test that produced a score of 250 or above. The figure appears to be a later estimate, repeated so often that it came to sound like fact.
Vos Savant: an old formula at work
The 228 figure is usually traced to a childhood test using the older ratio method, where IQ was calculated as mental age divided by actual age, times 100. Under that formula, a young child who performs like someone much older can get a huge number. A ten-year-old performing like a typical 22-year-old, for example, would score 220.
Ratio IQs behave very differently from modern scores, especially at the extremes, and Guinness eventually retired its highest IQ category, partly because such records could not be compared reliably.
Historical figures: educated guesses
In 1926, psychologist Catharine Cox published estimates of childhood IQ for hundreds of eminent historical figures, based on biographical records of what they achieved and when. It was an interesting exercise, but the results are informed guesses about people who never sat a test. Einstein's IQ, for the record, was never measured either. Our list of famous IQ myths covers that one in detail.
How modern IQ scores actually work
Today's major IQ tests use deviation scores. Your result is compared with a large, representative sample of people your age. The average is set at 100 and the standard deviation at 15. Each 15 points takes you one step further from the middle.
That makes very high scores extremely rare by design:
| IQ score | Standard deviations above average | Roughly 1 in |
|---|---|---|
| 115 | 1 | 6 |
| 130 | 2 | 44 |
| 145 | 3 | 740 |
| 160 | 4 | 31,500 |
| 175 | 5 | 3.5 million |
| 190 | 6 | 1 billion |
Each extra step makes a score dramatically rarer than the last.
Why scores above about 160 stop making sense
Now the maths starts to bite.
There aren't enough people to norm the test
To give someone a trustworthy score of 190, a test needs enough people at that level in its norming sample to know what "one in a billion" performance looks like. Real norming samples contain a few thousand people. At the far tail there may be nobody to compare against, so scores out there are extrapolations, not measurements.
Tests have ceilings
Widely used professional tests, such as the Wechsler scales, typically top out at a full-scale score of around 160. Beyond that, a person could answer every question correctly and the test simply has nothing harder to offer. It can tell you someone is at or near the top. It cannot tell you how far beyond it they go.
A score of 228 would be absurdly rare
On a modern deviation scale, 228 would sit more than eight standard deviations above average. That is far rarer than one in the entire population of the planet. Statistically, it is not a meaningful claim about a living person; it is a sign that a different kind of scoring was used.
Small errors become big ones
Every test has measurement error, and it grows at the extremes, where there are few items hard enough to separate people. A bad night's sleep or a lucky guess on the last few questions can move a very high score noticeably.
What about high-IQ societies and "power tests"?
Some groups beyond Mensa use their own unsupervised, untimed tests and report scores of 180, 190 or higher. These tests can be fiendishly difficult, but most have never been normed on a representative population, so their scores can't be translated into true rarity. They are better seen as hard puzzles with a scoring key than as clinical-grade measurements. If you are curious about the better-known societies, our article on the Mensa IQ requirement explains how they set their entry bar.
So who really has the highest IQ?
The honest answer is that nobody knows, and current tests cannot tell us. What we can say is:
- Many people have scored at or near the ceiling of major tests.
- Among those people, tests can't reliably rank who is "higher."
- Claims well above 200 come from old ratio formulas, unnormed tests or guesswork.
- Exceptional achievement, like Tao's mathematics, tells you far more about a person's ability than any inflated number.
What this means for your own score
The useful lesson here is about precision. IQ tests are most accurate in the middle of the range, where most people are, and least accurate at the very edges. A score is best read as a range: something like "probably between 118 and 128" rather than exactly 123.
If you want a sensible sense of where your reasoning sits, take our free IQ test and treat the result as an estimate, not a label. And if you are wondering where "genius" begins, our guide to what IQ counts as genius explains why the line is blurrier than most people expect.
The bottom line
The highest IQ scores you see online, from 228 to 300, come from outdated ratio formulas, unnormed tests or historical guesswork. Modern tests set the average at 100 and generally top out around 160, beyond which there simply isn't enough data to measure anyone precisely. The real answer to "who has the highest IQ?" is that nobody can say.
FAQ
What is the highest IQ score a test can give?
Most major professional tests top out at around 160 for adults. Some have extended norms that reach higher, but those scores become less reliable the further they go.
Did Marilyn vos Savant really have an IQ of 228?
That figure comes from an older ratio-style calculation from childhood testing. It cannot be compared with modern deviation scores, which would make 228 statistically implausible.
Is an IQ of 200 possible?
On a modern scale with an average of 100 and a standard deviation of 15, a score of 200 would be rarer than one in many billions. No current test can measure that level reliably.
What was Einstein's IQ?
Einstein never took an IQ test. Any number attached to him is an estimate, not a measurement.
