IQ Percentile Calculator

IQ stands for Intelligence Quotient and is a numerical measure of a person's reasoning and problem-solving ability relative to the general population. Tests are standardized so that the average score is 100 with a standard deviation of 15. A score above 100 means you performed better than average, and a score below 100 means you performed below average.

Your IQ percentile is calculated using the cumulative normal distribution. With a mean of 100 and a standard deviation of 15, you convert your IQ score to a Z-score ((IQ - 100) / 15) and then look up the cumulative probability. For example, an IQ of 120 gives a Z-score of 1.33, which corresponds to roughly the 91st percentile.

A percentage is a ratio out of 100 (e.g., you answered 80% of questions correctly). A percentile rank tells you what proportion of the population scored below you — if you're in the 91st percentile, you scored higher than 91% of people, not that you answered 91% of questions correctly.

With a standard deviation of 15, an IQ of approximately 135 corresponds to the 99th percentile, meaning you scored higher than 99% of the population. With Cattell's SD of 24, the equivalent score would be around 156.

Generally, an IQ of 130 or above (top 2% of the population) is considered 'very superior' or 'gifted.' Mensa, the high-IQ society, requires a score in the top 2%, which is typically an IQ of 132 or higher on the Wechsler scale. An IQ above 145 is considered 'profoundly gifted' and is extremely rare.

The upper 2% corresponds to an IQ of approximately 130 on the standard Wechsler scale (SD=15). This is the threshold used by Mensa for membership. On the Cattell scale (SD=24), the equivalent score would be around 148.

An IQ of 150 on the standard scale (SD=15) places you at approximately the 99.96th percentile — roughly 1 in 2,330 people. It is an exceptionally rare score. Most standardized IQ tests are not designed to measure scores this high with precision, so results at the extreme ends should be interpreted cautiously.

IQ tests are among the most reliable and valid psychological assessments when administered under standardized conditions. However, scores can be influenced by factors such as test anxiety, cultural background, education, and the specific test used. A single IQ score should be interpreted as an estimate within a range, not an exact fixed number.