The Highest IQ Ever Recorded: Who Has the Highest IQ in the World?

The highest IQ ever officially recorded belongs to Marilyn vos Savant, whom Guinness World Records once listed at 228 — but that number comes from a childhood ratio-IQ score that modern testing cannot reproduce, and Guinness retired the category in 1990 for exactly that reason. Every figure you'll see above roughly 160 — for vos Savant, William James Sidis, Terence Tao or anyone else — is either an old ratio score, a retrospective estimate, or an unverified claim. Modern, properly normed IQ tests simply don't go that high. Here's what the famous numbers actually mean, and why the honest answer to "who has the highest IQ in the world" is: nobody can say.

What is the highest possible IQ score?

On a properly normed modern test, the highest IQ score you can actually get is roughly 160 — that is the top of the standard reporting range for instruments like the WAIS-IV and Stanford-Binet 5, not a limit on human ability. Scores above it aren't "impossible" so much as unmeasurable: there is no way to norm them reliably, and the test runs out of questions hard enough to tell one exceptional person from another.

That is why the highest recorded IQ figures you see quoted — 228, 250, 276, 300 — never come from a modern test. They come from one of three places: the obsolete ratio scoring used before deviation scoring replaced it, a retrospective estimate someone made after the fact, or an unstandardized high-IQ-society questionnaire that was never normed on a general population. The table below sorts the best-known claims into those categories.

The highest IQ scores ever claimed, ranked

People usually want this as a list, so here is one — ordered by the headline figure most often quoted for each name. Read it as a ranking of claims, not of people: only one entry on it was ever recognised by a record-keeping body, and none of the top six comes from a modern normed test.

1. William James Sidis — 250–300. A posthumous estimate, never a test result.
2. YoungHoon Kim — 276. From high-IQ-society questionnaires that were never normed on a general population.
3. Terence Tao — 211–230. An estimate from childhood achievement. The name most often attached to "highest IQ mathematician".
4. Marilyn vos Savant — 228. The only figure here any record-keeping body ever listed, and it is a childhood ratio score on an obsolete scale.
5. Christopher Hirata — 225. A widely repeated estimate with no test, year or administrator named.
6. Kim Ung-yong — 210. A childhood score under the same pre-1990 Guinness regime as vos Savant.
7. Christopher Langan — 195–210. Figures from media profiles and unstandardized instruments; no normed clinical score has been published.
8. Albert Einstein — 160+. He never took an IQ test. The number is invented.
9. Stephen Hawking — 160. Unsourced, and Hawking publicly dismissed the question.
10. Elon Musk — 155. An unsourced listicle figure; no test result has ever been published.

So if you are asking who has the fourth or fifth highest IQ, the honest answer is that the question has no factual answer — you are asking which unverified claim someone wrote down fourth. The one thing the list does establish is that every figure on it above 160 sits outside what any current test can measure, which is the subject of the rest of this page.

Marilyn vos Savant and the Guinness record

Marilyn vos Savant entered the Guinness Book of World Records in 1985 under "Highest IQ" with a score of 228. The figure came from a Stanford-Binet test she took at age 10 in 1956, scored the old ratio way: mental age divided by chronological age, multiplied by 100. She answered questions at the level of an average 22-year-old's mental age while being 10 years old — hence roughly 228.

The problem is that ratio IQ and modern IQ are different measurements that happen to share a name. A ratio score of 228 does not mean she outscored 99.9999999% of adults; it means she was extraordinarily far ahead of other 10-year-olds. Modern tests use deviation scoring instead — your score reflects where you stand on the bell curve relative to your own age group, with a mean of 100 and a standard deviation of 15 (see our guide to the average IQ for how that works). Ratio and deviation scores aren't convertible, especially at the extremes. Guinness recognized this and retired the "Highest IQ" category entirely in 1990. Vos Savant remains a genuinely brilliant person — her long-running column famously handled the Monty Hall problem correctly while thousands of PhDs wrote in to disagree — but the 228 is an artifact of an obsolete scoring method, not a measurement any current test could produce.

William James Sidis: the 250–300 myth

William James Sidis (1898–1944) is the internet's favorite candidate for "smartest person ever," usually with an IQ quoted between 250 and 300. He was a real and remarkable prodigy: he entered Harvard at 11, lectured on four-dimensional bodies to the Harvard Mathematical Club, and reportedly worked with dozens of languages. But the IQ figure attached to his name is a retrospective estimate, made after his death and popularized by his sister and later writers — not a documented score from any standardized test. There is no verified record of Sidis ever sitting a proper IQ test. His story says a lot about prodigy, pressure and privacy; it says nothing measurable about the upper limit of human IQ.

Terence Tao, Kim Ung-yong and modern claims

Terence Tao, the Australian-American mathematician who won the Fields Medal at 31, is routinely cited with an IQ of 211–230. Again: this is an estimate, not a verified score from a normed test. What is documented is arguably more impressive — Tao scored 760 on the SAT math section at age 8 and remains one of the most productive mathematicians alive. Kim Ung-yong, a Korean former child prodigy, was listed by Guinness with an IQ of 210 under the same pre-1990 regime that listed vos Savant; the score reportedly derives from childhood testing and carries the same ratio-versus-deviation caveat. Kim himself has spent much of his adult life pushing back on the "failed genius" narrative, pointing out that a happy, ordinary career is not a tragedy.

Famous IQ claims: verified or not?

Why the highest IQ score on modern tests is about 160

Modern tests like the WAIS-IV and Stanford-Binet 5 report standard scores up to roughly 160. This isn't timidity — it's statistics. Because IQ is a rank on the bell curve, extreme scores correspond to extreme rarity: an IQ of 160 is four standard deviations above the mean, roughly 1 person in 31,000 — far beyond even the Mensa admission threshold of 132–148 depending on the test. An IQ of 180 would be about 1 in 20 million; 190 would be around 1 in a billion. To norm a test at those levels you would need to find and test enormous samples of people who all score at the very top of every existing measure — which is practically impossible. Above the ceiling, the test also runs out of discriminating items: once someone answers essentially everything correctly, the instrument can't tell a 1-in-31,000 mind from a 1-in-20-million one. Our IQ percentile and rarity table shows how quickly rarity explodes past 145, and the IQ scale guide explains what the top classification bands mean and how the standard ranges compare.

Can anyone have an IQ of 300, 500 or 5,000?

No — and the reason is arithmetic rather than opinion. A modern IQ is a rank on a bell curve with a mean of 100 and a standard deviation of 15, so every score is really a statement about rarity. Once you write down a number, the rarity it implies is fixed, and past about 200 those rarities stop describing anything that could exist.

• IQ 200 is about 1 in 76 billion. Roughly 117 billion people are estimated to have ever lived — so across all of human history you would expect around one person to reach it.
• IQ 300 is about 1 in 10⁴⁰ — a 1 followed by forty zeros. You would need vastly more people than the universe has ever contained to expect a single one.
• IQ 325 is about 1 in 10⁵⁰, comparable to picking one specific atom out of the entire Earth.
• IQ 700 is about 1 in 10³⁴⁹, and IQ 5,000 is 1 in a number with more than 23,000 digits.

Numbers like these circulate because they sound impressive and because nothing stops anyone from typing them. But they are not high scores on the IQ scale — they are outside it. No instrument produces them, no norming sample could support them, and a figure whose implied rarity exceeds the number of humans who have ever lived is not a measurement of anyone. That is also why the mythic historical figures — 228, 250, 276, 300 — all trace back to ratio scoring, estimates or questionnaires rather than to a normed test.

What is the lowest possible IQ score?

About 40 on the standard scoring of most modern tests — and no lowest IQ has ever been verifiably recorded. That is structural rather than a gap in the record-keeping: every standardized test has a floor as well as a ceiling. The Wechsler scales and the Stanford-Binet 5 report standard scores down to 40; the DAS-II, a children's battery, stops at 30, the lowest point its General Conceptual Ability scale can express. Someone who answers nothing correctly does not score zero — they score the floor, and so does the next person. The instrument stops discriminating before the scale runs out.

The floor is a property of the scoring method rather than a wall, which is the last reason a "lowest IQ" number cannot mean what people take it to mean. The Stanford-Binet 5 offers an Extended IQ scale that stretches the reportable range from 40–160 out to 10–225, built precisely so researchers can tell apart people whose standard scores all pile up at the floor. Those extended scores are rare, carry far wider measurement error than ordinary ones, and are not what a standard report shows.

That floor is why a "lowest IQ ever" figure cannot mean what a highest-IQ figure means. At the very bottom of the range the number stops separating one result from another, which is why assessments there rest on everyday functioning rather than on the score — and where a test cannot tell two results apart, no record can be set between them.

An IQ of 0 is not a thing either, for the same reason an IQ of 5,000 is not: the scale is a rank against a population, not a quantity that can run out. Zero would have to mean a percentile below the lowest human, and the scale has no way to express that. Figures do circulate online as "the lowest IQ ever recorded", usually pinned to a named person and repeated without a source; none traces to a psychometric record, so this page does not repeat them — the same standard applied to the celebrity claims further down. For what individual scores below the average actually mean, band by band, see the low end of the IQ scale.

Who is the smartest person in the world?

Nobody can answer this, and no organisation tracks it. Guinness World Records retired its "Highest IQ" category in 1990 and nothing replaced it, so there is no register, no title and no current holder. Even if there were, an IQ test could not settle it: above roughly 160 the instruments stop discriminating, so the people at the top of the measurable range are indistinguishable from each other by test score alone.

The question also quietly swaps two different things. IQ measures a specific band of reasoning ability under timed conditions; being the smartest person in the world, in the sense people usually mean, involves judgement, creativity, knowledge and output that no single number captures. That is why the names that come up — Tao, Sidis, vos Savant, Langan — are famous for what they did or for a story attached to them, not for a verified score. The most defensible answer is that the smartest person in the world is unidentified and unidentifiable, and anyone confidently naming one is ranking claims, not people. (A related question — which personality type scores highest — is handled separately in the smartest personality type.)

Who has the highest IQ in the United States?

There is no official answer for the United States either — but the only figure any record-keeping body ever listed belongs to an American. Marilyn vos Savant, born in St. Louis, held the Guinness "Highest IQ" listing at 228 until the category was retired in 1990, and no American (or anyone else) has held an official title since. The other names most often quoted in answer to "who is the smartest person in America" are Christopher Langan — whom media profiles have called exactly that, on figures of 195–210 from unstandardized instruments — and the astrophysicist Christopher Hirata, whose widely repeated 225 names no test, year or administrator. Every caveat on this page applies unchanged at the national level: the claims above 160 are estimates or obsolete ratio scores, and no modern normed test can adjudicate between them.

A different question hides behind the same words: if you are asking about the average IQ across the United States or how the states compare, that is a statistics question rather than a record-holder question — our guide to the average IQ in the USA covers it, including why the popular state and national rankings disagree with each other.

Celebrity IQ lists are mostly fiction

Search any famous name plus "IQ" and you'll get a confident number. Almost none of these are sourced to a documented, professionally administered test. They propagate from listicle to listicle until repetition looks like evidence. Einstein never took an IQ test — the 160 attached to him is invented. The same goes for most figures quoted for actors, entrepreneurs and world leaders. When a celebrity score is real, it's usually a childhood school test filtered through decades of retelling. A useful rule: if no one can name the test, the year and who administered it, the number is decoration.

These are the celebrity IQ figures people look up most often, and what is actually on record for each. In every case the honest entry in the last column is the same, which is itself the finding:

The pattern is worth stating plainly: the figures quoted for entertainers are almost always higher than the ones on record for Nobel laureates, because the entertainer numbers were made up and the scientist numbers were not. A confident celebrity IQ number is evidence about the website publishing it, not about the person.

Where the IQ numbers for historical geniuses come from

There is a second kind of list, and it looks far more respectable than the celebrity one: Goethe at 210, with Newton, Leonardo, Mozart and Napoleon each carrying a number of their own. Those figures were not invented the way the celebrity ones were. Nearly all of them come from a single source — a 1926 doctoral dissertation by Catharine Cox, published as Volume II of Lewis Terman's Genetic Studies of Genius. None of those people were ever tested. Cox estimated what each might have scored as a child by reading their biographies, more than 3,000 of them, in several languages.

How that list was built matters more than any number in it, and three of its rules explain most of what it can and cannot tell you.

It was never a list of the smartest people in history. Cox began from a ranked list of the thousand most eminent figures compiled in 1903, took the top half, and kept only those born between 1450 and 1850 whose childhoods were documented in detail. William Shakespeare was cut for lack of childhood records. Hereditary rulers such as Louis XIV were cut because their eminence was inherited rather than achieved. What survived is the set of eminent Westerners of four centuries whose early lives happened to be well written up — a fact about surviving paperwork as much as about minds.

Each person received four estimates, not one. Cox's raters produced one estimate from the record up to age 16 and another from ages 17 to 26, each in a raw and a corrected form. The single confident number on a listicle is one of those four, almost never labelled as to which.

Cox measured how good each biography was, and published it. She gave a reliability coefficient for every one of the 301 subjects, acknowledging openly that they did not all have equally good data, and used those coefficients to calculate the corrected estimates. Where the surviving record was thin, the estimate came out low — which makes a low score on this list partly a statement about an archive. The highest figure in her table is Goethe's 210; the "210–225" that circulates online blends her estimate with later compilations built on different methods.

The estimates are also not measuring the same thing from one person to the next. Mozart's rests largely on his musical development, Pascal's on his mathematical development. A modern IQ test deliberately samples a broad and generic set of abilities; Cox's raters worked with whatever each childhood happened to leave behind.

The finding the lists leave out is the one Cox herself cared about. Across all 301 subjects the average uncorrected childhood estimate was 153. But the correlation between her estimated IQ and achieved eminence was 0.25, and 0.16 once she adjusted for how reliable each biography was — real, but modest. Her own conclusion was that persistence did as much of the work as intellect: eminence went to those with high but not the highest intelligence, combined with the greatest degree of persistence. Of every group she examined, military leaders scored lowest.

Why these numbers are everywhere has itself been documented. Dean Keith Simonton, who has worked with Cox's data for decades, observed in 2020 that searching almost any historic genius's surname together with "IQ" will very probably return one of her estimates. A century on, a graduate student's careful and heavily qualified guesses circulate as though somebody had administered a test.

What extremely high scores actually tell you

Within the measurable range, higher scores do predict real outcomes — academic achievement, job performance in complex roles — but the relationship is statistical, not a destiny, and past roughly 130 (the top ~2%, covered in what counts as a high IQ) differences in drive, opportunity and specific skills matter at least as much as further IQ points. It's also worth remembering that online IQ tests, including ours, produce estimates for self-knowledge and training — not clinical diagnoses, and certainly not world records. If a website tells you your IQ is 187, it is measuring your willingness to share the result, not your intelligence.

The honest bottom line: the highest verified scores on modern tests sit at the instruments' ceilings around 160, held by more people than you'd think and publicized by almost none of them. The mythic numbers — 228, 250, 300 — belong to a scoring system we abandoned decades ago, and to stories we like telling about genius.

A record score and an island of ability are two different things. Where a full-scale IQ is high across the board, savant syndrome describes a profile in which a single ability stands far above everything else — a shape, not a ranking.

IQ Revealed is not affiliated with, endorsed by or connected to Pearson, Riverside Insights, Mensa, Guinness World Records or any publisher of the tests named on this page, and does not administer or score them. They are named only so that the score ranges and record claims discussed above can be traced back to where they actually come from.