IQ Score Percentile Calculator
Calculate the percentile for any IQ score using the normal distribution.
Enter an IQ score to see what percentage of people score at or below that level.
IQ scores are standardized to follow a normal (bell curve) distribution with a mean of 100 and a standard deviation of 15. This means roughly 68% of people score between 85 and 115, and about 95% score between 70 and 130.
The percentile tells you what percentage of people score at or below a given IQ. A score at the 75th percentile means you scored higher than 75% of the population — 75 out of 100 people score lower.
Percentile = Φ((IQ - 100) / 15) x 100
Where Φ is the cumulative distribution function (CDF) of the standard normal distribution. The z-score is (IQ - 100) / 15.
Classification labels vary by source, but a common system:
- Below 70: Extremely low (less than 2nd percentile)
- 70-79: Borderline (2nd-9th percentile)
- 80-89: Low average (9th-25th percentile)
- 90-109: Average (25th-73rd percentile)
- 110-119: High average (73rd-91st percentile)
- 120-129: Superior (91st-97th percentile)
- 130-139: Very superior (97th-99.5th percentile)
- 140+: Gifted / Genius range (above 99.5th percentile)
Mensa accepts the top 2% — roughly IQ 130 and above on most scales.
One important caveat: different IQ tests use different scales. The Stanford-Binet and Wechsler tests both use mean=100, SD=15. The Cattell Culture Fair test uses mean=100, SD=24. This calculator uses the standard SD=15 scale. A score of 130 on a Cattell test is roughly equivalent to 120 on a Wechsler test.
IQ measures specific cognitive abilities assessed by tests, not general intelligence in a broader sense. It is a useful but incomplete picture.