IQ Percentile Calculator
Enter an IQ score to see what percentile of the population it falls into, based on the standard bell-curve model used by most IQ tests.
How This Calculator Works
Most IQ tests are designed so that scores follow a normal (bell-curve) distribution with a mean of 100. This calculator converts any IQ score into a percentile rank — the share of the population that would be expected to score at or below that value — using the standard normal cumulative distribution function.
The Method
The score is first converted to a z-score using z = (IQ – 100) / SD, where SD is the test’s standard deviation (15 for most modern tests such as the WAIS and WISC, or 16 for the Stanford-Binet scale). The z-score is then passed through the standard normal cumulative distribution function to produce a percentile rank.
Things to Keep in Mind
- This tool assumes a perfectly normal distribution, which is a simplification — real test norms can differ slightly at the extreme ends of the scale.
- Different tests use different standard deviations, so always check which scale your score comes from.
- This calculator is provided for general educational and planning purposes only and is not a substitute for interpretation by a qualified psychologist.