How Rare Is an IQ of 140? (And 145, 150, 160)

The rarity of each score

IQ	Share of people at or above	About 1 in…	Common label
130	2.3%	44	Very superior / gifted
135	1.0%	102	Gifted
140	0.38%	261	Gifted / “genius” in old tables
145	0.13%	741	Highly gifted
150	0.043%	2,330	Highly gifted
155	0.012%	8,137	Exceptionally gifted
160	0.0032%	31,560	Exceptionally gifted

In a city of one million adults, that works out to roughly 3,800 people at 140 or above, 1,350 at 145 or above, and about 30 at 160 or above. The full table for every score is in our IQ percentile chart.

Where the number 140 comes from

The “140 = genius” idea dates to Lewis Terman’s 1916 Stanford-Binet manual, which labelled scores of 140 and up “genius or near genius”. The label was dropped decades ago; modern manuals stop at “very superior” or “extremely high”, and gifted-education programmes typically use 130 (the top 2%) as the entry line. Nothing changes at exactly 140 except the word people attach to it.

A more useful way to think about 140 is in standard deviations: it is 2.67 SD above the mean. At that distance, a test with a reliability of 0.95 still has a standard error of about 3.4 points, so the honest statement is “somewhere between the mid-130s and the mid-140s”.

Why scores above 145 are estimates

Norm samples are finite. A test standardised on 2,000 people contains, on average, only three people at 145 or above and almost certainly nobody at 160. Publishers extend the top of the scale by assuming the normal curve continues, which is reasonable but unverified. Real distributions also have slightly heavier tails than the pure normal curve, so the true share at 160+ is probably a little higher than 1 in 31,000. Either way, a test cannot distinguish 155 from 165 with any confidence: at that level, ceiling effects (running out of hard questions) dominate.

This is also why claims of IQs of 200 or more in biographies are not measurements in the modern sense. They come from the old ratio formula (mental age divided by chronological age), which produces huge numbers for precocious children and has no meaning for adults. The history is in what mental age really is.

Can an online test tell you whether you are at 140?

A well-built online test can place you in the right region: top 10%, top 2%, or above. What it cannot do is resolve the difference between 138 and 143, because that needs many very hard, well-calibrated items and a supervised setting. Our Mensa-style practice test is designed for the top end (35 matrix puzzles, 25 minutes) and tells you whether you cross the top-2% line; the 45-question full test gives the narrowest confidence interval of our free tests. For a formal number that an institution will accept, a psychologist-administered WAIS or Stanford-Binet is the route.

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