High-IQ societies and what it takes to join

Mensa is by far the oldest and largest. Founded in Oxford in 1946 by Roland Berrill and Lancelot Ware, it now runs as national groups under Mensa International. The other societies were mostly founded later by people who wanted a narrower slice of the curve. Each sets its bar as a percentile, so the score you need depends on which test you took.

Enter a score and the scale of the test it came from. Scales matter: a Cattell 148 and a Wechsler 130 are the same rank. If you are not sure of the scale, our standard deviation guide lists which tests use which.

Every society insists on a recognised test taken under supervision, and each publishes its own list. In practice there are three routes.

• An individual test with a psychologist, such as the WAIS, WISC or Stanford-Binet. Accepted by all of them if the score clears the bar, with a copy of the report.
• The society's own supervised test. Mensa runs admission sessions in most countries. This is the cheapest and most common route into Mensa; the higher societies generally do not run their own.
• Old admissions and aptitude scores. Some societies accept scores such as the SAT, GRE or LSAT from specific years at a stated percentile. The years matter, because these tests changed and were recentred. Check each society's current list before sending anything.

Professional tests are normed on samples of about 2,000 to 2,200 people. In a sample that size you would expect about three people above 145 and nobody above 160. Scores at the Prometheus and Mega levels are therefore extrapolated from the shape of the curve, not counted from real people who scored that high, and the tests' ceilings sit close to those levels anyway.

This is why the Prometheus and Mega societies have historically leaned on specially written "high-range" tests, often untimed and unsupervised, whose norms are thin. That is not a reason to sneer at them, but it is a reason to read a claimed 170 as "very high, imprecisely measured". Our IQ rarity calculator explains why any rarity beyond about 145 to 160 should be read as a rough guide.

That depends on what you want. Members describe the appeal as social: local meet-ups, special-interest groups, and the relief of talking to people who enjoy the same kind of puzzles. None of the societies is a credential employers ask for, and membership says nothing about achievement. Mensa's size makes it the practical choice for meeting people; the higher societies are small and mostly online.

If your aim is simply to know your number, a supervised test is the honest way to get one. Our guide on how to find out your IQ compares the routes, and what to expect from the Mensa test covers the most common one.