Estimate, not a test
Barthold Georg NiebuhrHistorian
Cox rated him 175 for ages 17 to 26, 2 points above 173. Cox's childhood rating for him was 165.
What does a 173 IQ mean?
A 173 IQ means a score higher than about 99.999943% of people, roughly 1 in 1,762,173. It also has a place in the history of high-IQ societies: when the Mega Society was formed, people scoring 173 or more on Kevin Langdon's Adult Intelligence Test were invited to join.
99.999943rdpercentile
1 in 1,762,173score 173 or higher
Exceptionally giftedlevel of giftedness
173IQ scoreTop 0.000057%
173 on the IQ bell curve
At 73 points above the mean of 100 (4.87 standard deviations), 173 sits where the curve has almost flattened onto the axis. Only 0.000057% of people score here or higher; on the left chart that group is the barely visible orange edge.
About 4,660 people in the world would score 173 or above on a perfect bell curve, about the population of a large village.
Reading an IQ of 173
The Langdon Adult Intelligence Test, or LAIT, was one of the early unsupervised high-range tests. According to the Mega Society, its qualifying score was later raised from 173 to 175, and "official scoring of the LAIT terminated at the end of 1993, after the test was compromised". The pattern is the same as for later home tests: once answers spread, the scores stop meaning anything.
On the standard bell curve, 173 is about 1 in 1.76 million, so a society asking for one in a million should, in principle, have set its line a little lower. The fact that the bar moved shows how uncertain these very high scores are, even to the people designing the tests.
How many people have an IQ of 173?
How big a group do you need before someone in it is likely to score 173? About 1,762,173 people. Watch the crowd grow to that size.
A crowd of 1,762,173 people
1,762,173
One dot per person, and on average only one of them, shown in orange, scores 173 or more.
People scoring 173 or higher, by population
| Worldwide (8.2 billion people) | about 4,660 |
| India | about 831 |
| United States | about 194 |
| United Kingdom | about 39 |
| Canada | about 24 |
| Australia | about 16 |
Population: World Bank, total population, 2025. Counts assume the same bell curve in every country and are rounded. Real tests can't sort people this finely, as the next sections explain.
Which high-IQ societies accept an IQ of 173?
Entry to a high-IQ society depends on a percentile, which each one turns into a score per accepted test. Measured under supervision, 173 meets every one of these bars.
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MensaTop 2% (98th percentile) on an approved, supervised test130met
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IntertelTop 1% (99th percentile); lists a Wechsler full-scale IQ of 135135met
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Triple Nine Society99.9th percentile; lists a WAIS full-scale IQ of 146146met
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International Society for Philosophical Enquiry99.9th percentile; lists a WAIS-III or WAIS-IV full-scale IQ of 146146met
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Prometheus Society1 in 30,000 (99.997th percentile), four standard deviations above average160met
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Mega SocietyOne in a million, beyond the range of standard tests171met
Scores for Mensa, Intertel, Triple Nine and ISPE are the Wechsler figures those societies list or that match their percentile. Prometheus and Mega give only a rarity; the scores shown are the matching points on the standard scale. Prometheus says no test currently being given is approved for its entry. Online test results are not accepted by any of them.
Can an IQ test measure 173?
The adult Wechsler test and the Stanford-Binet 5 both stop at 160, so neither can give a 173. To report a score this high, a psychologist needs an extended scale, such as the WISC-V extended norms (to 210) or the Stanford-Binet 5 Extended IQ (to 225), shown in the bars below.
Why so uncertain? Because a test compares you with its norm sample, and the WAIS-IV sample had 2,200 adults. The bell curve expects about 0.0012 of them at 173 or higher. With nobody in the sample anywhere near this level, the number comes from the shape of the curve, not from comparison with real people.
There is measurement error too: a professional report would give a range of about 168 to 178 around a 173. With so few people ever measured at this level, the true uncertainty is larger still. Online results are far rougher, which is why ours stops at 145. Are online IQ tests accurate?
Sources: WAIS-IV range and norm sample from Canivez (2010), Mental Measurements Yearbook review; Stanford-Binet 5 and its Extended IQ from PRO-ED; WISC-V extended norms from Pearson Technical Report #6 (2019). Striped bars are extended scales, used only when a person hits the normal ceiling.
Converting an IQ of 173 between scales
The number attached to a result depends on the scale's standard deviation. Near 173, switching scales can add or remove dozens of points for exactly the same rank.
173standard scale (SD 15), used by Wechsler tests and on this page
178older Stanford-Binet scale (SD 16)
217Cattell scale (SD 24), used by some older and online tests
So a "173" isn't always a 173. On the Cattell scale it corresponds to about 146 on the standard scale; on an SD 16 scale, about 168. Why IQ scales differ.
Who has been rated near an IQ of 173?
Catharine Cox's 1926 study is the source of nearly every historical "IQ". She estimated each person's score from records of their early life, once for childhood and once for ages 17 to 26. None of them sat a test.
George BerkeleyPhilosopher
Cox rated him 175 for ages 17 to 26, 2 points above 173. Cox's childhood rating for him was 150.
Source: Cox, C. M. (1926), Genetic Studies of Genius, Vol. II: The Early Mental Traits of Three Hundred Geniuses, Stanford University Press. Cox stressed that thin records pull estimates down. Read more in where the historical genius IQ estimates came from.
From 606 to Mega: how the one-in-a-million societies began
The Mega Society, founded in 1982 by Ronald K. Hoeflin "to facilitate psychometric research", absorbed an earlier group, the 606 Society, named for "6 in 106". Holders of LAIT scores of 173 or more were invited to join; the qualifying score was later raised to 175.
Several tests were accepted in the society's early years before the LAIT and Hoeflin's Mega Test became the only official entrance tests. Both were eventually compromised. The history is a useful caution for anyone who sees a score in the 170s quoted online: ask which test produced it, and when.
Source: Mega Society, About the Mega Society.
What does an IQ of 173 mean?
A score of 173 means a rank of about one in two million for your age. It is beyond the ceiling of every standard clinical test, so in practice a 173 comes from an extended children's scale or a high-range test, and its exact value carries a wide margin.
Where 173 falls among the levels of giftedness
115–129Mildly gifted
130–144Moderately gifted
145–159Highly gifted
160–179Exceptionally gifted
180+Profoundly gifted
Levels and ranges from Gross, M. U. M. (2000), "Exceptionally and Profoundly Gifted Students: An Underserved Population", Understanding Our Gifted. They are a guide for education, not a ranking of people.
How far 173 is from other milestones
27 points above the Triple Nine and ISPE bar (146)a score of 173 is about 1,907 times rarer than 146
13 points above the ceiling of most professional tests (160)a score of 173 is about 56 times rarer than 160
2 points above the Mega Society's one-in-a-million level (171)a score of 173 is about 1.9 times rarer than 171
7 points below the start of the profoundly gifted band (180)reaching 180 is about 12 times rarer than 173
4.87 standard deviations above averageaverage is 100 and one standard deviation is 15 points
IQ 173 compared with nearby scores
| IQ | Percentile | Rarity | Level |
|---|---|---|---|
| 169 | 99.99978th | 1 in 473,383 | Exceptionally gifted |
| 171 | 99.99988th | 1 in 905,541 | Exceptionally gifted |
| 173 | 99.999943rd | 1 in 1,762,173 | Exceptionally gifted |
| 175 | 99.999971st | 1 in 3,488,556 | Exceptionally gifted |
| 177 | 99.999985th | 1 in 7,026,047 | Exceptionally gifted |
Your questions about a 173 IQ
Is 173 a high IQ?
Yes. 173 is a very high IQ: about 1 person in 1,762,173 scores this high or higher, which puts it at the 99.999943rd percentile. It is above the 130 that most definitions use for a high IQ, and at or above the 146 used by the Triple Nine Society for its 99.9th percentile entry.
What is an IQ of 173 on the Cattell scale?
About 217. The Cattell scale uses a standard deviation of 24 instead of 15, so the same result gives a bigger number. Going the other way, a Cattell score of 173 is only about 146 on the standard scale.
What percentile is an IQ of 173?
An IQ of 173 is at about the 99.999943rd percentile. Only about 0.000057% of people score 173 or higher.
How rare is an IQ of 173?
About 1 person in 1,762,173 scores 173 or higher, on the standard bell curve. Across the world's population of about 8.2 billion, that would be roughly 4,660 people.
Is an IQ of 173 good?
Yes, by any measure. 173 is higher than about 100% of people. Remember that a score this high needs a supervised professional test to be confirmed, and that it describes reasoning on a test, not every kind of talent.
What is the LAIT?
The Langdon Adult Intelligence Test was an unsupervised high-range test used by early high-IQ societies. The Mega Society once accepted LAIT scores of 173, later 175, but official scoring ended in 1993 after the test was compromised.
Related: what counts as a good IQ score, the highest IQ in the world, famous people's IQs and the full IQ scale and range chart.
An IQ test arrives at a score like 173 by combining several kinds of task. Learn more about verbal reasoning, processing speed, fluid vs crystallized intelligence, abstract reasoning and spatial reasoning, or try the free pattern recognition test.
Many famous IQ figures are guesses. See what is really known about Elon Musk's IQ, Garry Kasparov's IQ, Terence Tao's IQ, Einstein's IQ, Isaac Newton's IQ, Nikola Tesla's IQ, Stephen Hawking's IQ and Bill Gates' IQ.
Curious where you'd land?
Try the free Assessivo IQ test: 36 questions, about 25 minutes, and an estimated score up to 145. Confirming a result as high as 173 needs a supervised professional test.
Take the free IQ testPortraits are pencil-style sketches by Assessivo, based on: George Berkeley after John Smibert (about 1727), public domain.