IQ 200

200 is 6.67 standard deviations above the mean. On a bell curve that works out to about 1 in 76 billion people, which is fewer than one person in the entire world population. The bell curve is a model, though, and at this height it is doing most of the work.

No test has enough people in its norm sample to check its accuracy at 200. In a 2,200-person sample the bell curve expects effectively nobody at 200 or higher.

Real populations may not follow the bell curve perfectly in the far tails, so rarity figures this extreme are illustrations, not head counts.

Most very high numbers you see online come from one of a few sources, and knowing which one produced a 200 tells you how much weight to put on it.

• Historiometric estimates. Researchers such as Catharine Cox (1926) estimated IQs for famous people from biographies. Some of her adjusted estimates went above 200. They are educated guesses, not test results.
• Unnormed online quizzes. A test with no norm data can print any number. Very high outputs usually say more about the scoring than the person.
• Repetition without a source. Numbers attached to celebrities are often copied from site to site with no test report behind them.

Isaac Newton and Leonardo da Vinci are usually given estimates of 160 or more, and they are among 42 such profiles here. Only 1 goes as high as 200. All are judgements from biographies, not test results.

Two people with identical estimates can have very different evidence behind them. Each profile explains what its estimate is based on and how confident anyone can be.

Scoring 200 or higher is a 0.0000000013% share of everyone. Scaled up to whole populations, that works out as:

Going from 195 to 200 makes a score 9.2 times rarer, and going on to 205 multiplies the rarity by another 10. Near 200, each single point adds about 58% to the rarity.

What your 200 could really be. Even a good supervised test has a margin of error of roughly 5 points either side, and far more at this height. A true score from 195 to 205 would span rarities from 1 in 8.3 billion to 1 in 780 billion.

Which scale was it on? Score reports do not always say. On the common SD 15 scale your 200 stands as it is. If the report used SD 16 it equals about 194, and if it used SD 24 about 163. The percentile follows the converted number.

Estimates this high are reserved for a small group of scientists, artists and thinkers. These sit near 200. Treat these as informed guesses from biographies rather than results. Each profile sets out what its estimate rests on.

On a standard scale, 200 is six and two thirds standard deviations above the mean. The bell curve puts it at about 1 in 76 billion, which is fewer than one person in the entire world.

When you see 200 claimed, it is almost always a ratio IQ from childhood, a score on a scale with a wider standard deviation, or a historiometric estimate. None of those is equivalent to a modern adult test score of 200.

The scores one and five points either side of 200, plus the round numbers from 100 to 150, side by side. Tap any score for its full page.