IQ percentile calculator — find your ranking

An IQ score on its own is a number. What gives that number meaning is its position relative to the rest of the population. Percentiles provide this context: they tell you the percentage of people who scored at or below a given value. If you are in the 85th percentile, 85% of the norming population scored at or below your level.

Use the calculator below to convert any IQ score into its corresponding percentile, classification, and population comparison. The results are based on the standard normal distribution with a mean of 100 and a standard deviation of 15, which is the scoring model used by the Wechsler Adult Intelligence Scale and most modern IQ tests.

A percentile is a statistical measure indicating the value below which a given percentage of observations fall. In the context of IQ testing, the 50th percentile corresponds to an IQ of exactly 100 — the population mean. Half of all test-takers score above this point, and half score below.

Percentiles are not the same as percentages correct on a test. Getting 90% of questions right does not mean you are in the 90th percentile. Percentile rank is determined by comparing your score to the distribution of scores in the norming sample, not by the raw number of items answered correctly.

Percentiles are also distinct from standard scores. While an IQ score is a standard score (with defined mean and standard deviation), the percentile is its cumulative probability equivalent. The two convey the same underlying information in different formats, but percentiles are often more intuitive for non-specialists to interpret.

One of the most important features of the IQ-percentile relationship is that it is non-linear, especially at the tails of the distribution. Near the center of the bell curve, where most people cluster, small changes in IQ correspond to large changes in percentile. Moving from IQ 100 to IQ 105 shifts you from the 50th percentile to roughly the 63rd — a jump of 13 percentile points from just 5 IQ points.

At the extremes, the opposite occurs. Moving from IQ 135 to IQ 140 shifts you from approximately the 99.0th percentile to the 99.6th — a difference of only 0.6 percentile points for the same 5-point IQ increase. This is because the normal distribution has thin tails: very few people score in the extreme ranges, so each additional point represents a vanishingly small segment of the population.

This non-linearity means that percentile comparisons become less meaningful at the extremes. The difference between the 50th and 60th percentile is far more practically significant than the difference between the 99th and 99.5th percentile. For a detailed breakdown of score ranges, see the IQ scale and score chart.

The percentile for a given IQ score is derived from the cumulative distribution function (CDF) of the normal distribution. The process involves converting the IQ score to a z-score using the formula: z = (IQ - 100) / 15. The z-score represents how many standard deviations the score is from the mean. The CDF then gives the probability that a randomly selected person from the population would score at or below that z-value.

For example, an IQ of 115 yields a z-score of 1.0. The CDF at z = 1.0 is approximately 0.8413, so an IQ of 115 falls at the 84th percentile. An IQ of 130 yields z = 2.0, and the CDF gives approximately 0.9772 — the 98th percentile. For a deeper exploration of the mathematics, see how IQ is calculated.

Percentiles provide a frame of reference, but they should not be over-interpreted. A percentile ranking tells you where a score falls in a distribution. It does not tell you what a person can or cannot do. The difference between the 70th and 75th percentile is statistically real but practically negligible in most real-world contexts.

Percentile rankings are most useful at the extremes, where they can inform clinical or educational decisions. Scores below the 2nd percentile (IQ below 70) may indicate intellectual disability and warrant further assessment. Scores above the 98th percentile (IQ 130 or higher) may qualify an individual for gifted education programs or membership in organizations like Mensa.

It is also worth noting that percentiles from different tests are only comparable when both tests use the same norming model (mean 100, SD 15). Some tests, such as the Cattell III B, use a standard deviation of 24, which produces numerically higher scores for the same percentile. Always check the scoring scale before comparing results across tests. For more on how different scales relate, see what is IQ.