Where do individual IQ tests stop?
Main individual IQ tests stop at 160. Their stated full-scale ranges run from 40-160. This is the upper end of the scores those tests cover, not a measure of the limits of human ability.
A result at the top of a test's range can still be interpreted within that range. The IQ 160 page explains what that score means. A number beyond the range does not have the same test-based support, even if it is written with precision.
What does the rarity curve show?
The rarity curve estimates how uncommon high scores would be if the score distribution continued beyond the range covered by tests. It estimates 1 in 741 at or above 145, 1 in 32,000 at or above 160, 1 in 3,500,000 at or above 175, 1 in 1,000,000,000 at or above 190, and 1 in 76,000,000,000 at or above 200.
These figures describe a mathematical model, not people tested and found to have those scores. Each estimate extends the same curve farther beyond the measured range. The IQ standard deviation page explains the scale used to calculate rarity.
Why can’t tests rank people above the ceiling?
Tests cannot rank people reliably above the ceiling because norm samples have too few people at those score levels. A norm sample is the group used to set and interpret a test's scores. To compare individuals at the top end, the sample would need to cover that part of the range.
A curve estimates where a score falls under a model, but it does not supply observed test results. Without enough people in the sample at that level, the test cannot show how one person's result compares with another's. That is why a projected rarity and an individual ranking are different things.
Are claims of 200 or more measured IQ scores?
Claims of 200 or more are not measurements from the main individual tests. Their score ranges end before that point, and the norm samples do not include enough people at those levels to rank individuals there.
A number alone does not show which test supports it or whether that test covers the score. The curve's estimate for 200 describes a hypothetical frequency if the distribution continued. It does not confirm that anyone earned that score on a test normed across that range.
How should you read an extreme IQ number?
To read an extreme IQ number, check which test produced it and whether the test covers that part of the scale. Inside its range, a score compares performance with the test's norm group. Outside it, the test cannot support that comparison.
IQClock's free timed reasoning test does not print an IQ number. It presents reasoning questions; a normed individual test is used to compare results with a norm group. Keep those two kinds of results separate when reading a score or a claim about one.