I recently got curious about the distribution of IQ scores. For each IQ range, what is the corresponding percentile? Here is what I found using various internet sources.

The scores below are from the Stanford-Binet test.

132 - 98% - Mensa (approx 2 standard deviations)
136 - 99% - Intertel
141 - 99.5% - Poetic Genius
150 - 99.9% - Triple Nine, Glia (approx 3 standard deviations)
160 - 99.997% - Prometheus

Beyond 150 on a Stanford Binet test the percentiles are debatable. But they probably don't even make sense anyway for a couple of reasons.

First, most standard tests have ceiling effects with scores above 140. That means somebody gets all the questions right and his score is merely an age adjustment. Age adjustments assume mental performance is optimal in one's 20s and 30s with correction factors beyond that. The idea is that the very young have not yet learned to use their full capacity, and people gradually lose brain function past that age. Of course, the fact that the hardware gradually degrades is incontrovertible, but one may certainly question whether improvements in the software compensate for that.

Second, the distribution of IQ scores is not necessarily gaussian. As we get further from the mean of 100, the percentiles are harder to compute because so few people have such high scores that the samples are too few to produce reliable numbers. Also, different tests that have similar distribution around 100 often have widely varing distributions at the extremes.

It's worth mentioning that the uniqueness of high scores is often overstated. Consider a 150 IQ. Sounds really high if you call it "triple nine" or 3 standard deviations from the norm. But it means 1 of 1000. In our country of 300 million people, there are 300,000 with an IQ of 150 or higher. Put that way, it doesn't sound so unique or exclusive anymore.

What it boils down to is that anything over 140 is simply "very smart" and further categorization or comparison is difficult.