IQ Percentile Calculator

Convert an IQ score to a percentile ranking, z-score, and classification using the standard normal distribution.

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Result

Enter a value Enter an IQ score above to see the percentile ranking.

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IQ score to percentile ranking, z-score, and classification

An IQ percentile calculator converts any IQ score into a percentile ranking that shows where the score falls relative to the general population. Enter an IQ score to see the percentile, z-score, and standard classification instantly.

How IQ scores map to percentiles

IQ scores follow a normal distribution with a mean of 100 and a standard deviation of 15 on the most widely used scales (Wechsler, Stanford-Binet). A score of 100 means the person performed at the median — exactly at the 50th percentile. Each 15-point shift moves the score one standard deviation away from the mean.

The percentile is calculated using the cumulative distribution function (CDF) of the normal distribution. A score of 115 corresponds to roughly the 84th percentile, meaning the person scored higher than about 84 out of every 100 people. A score of 130 reaches approximately the 98th percentile.

z = (IQ − 100) / 15

The z-score measures how many standard deviations the IQ score is from the mean.

Standard IQ classifications

Psychologists use classification bands to describe score ranges. Scores between 90 and 109 are labelled Average, 110–119 High Average, 120–129 Superior, and 130 or above Very Superior. On the lower end, 80–89 is Low Average, 70–79 Borderline, and below 70 Extremely Low.

These classifications are guidelines rather than rigid labels. Performance on a single test can be influenced by test anxiety, fatigue, cultural factors, and practice effects. A clinical psychologist interprets scores in the context of a full assessment, not in isolation.

Frequently asked questions

What percentile is an IQ of 120?

An IQ of 120 corresponds to approximately the 91st percentile, meaning the person scored higher than about 91% of the population.

 Is IQ score the same as percentile?

No. IQ is a scaled score with a mean of 100 and standard deviation of 15. Percentile is the proportion of people who score at or below that IQ. They are related through the normal distribution but express different things.

 Can IQ scores change over time?

Yes. IQ scores can fluctuate by several points between test sessions due to practice effects, motivation, health, and other factors. Childhood IQ tends to stabilise in adolescence but is not perfectly fixed.

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