IQ Percentile Calculator
Any score, any scale, converted to percentile and rarity — exactly.
Percentile
84%
score at or above 84% of people
Rarity
1 in 6
score this high or higher
Classification
High average
A percentile is the plain-language reading of an IQ score: the share of people scoring at or below it. It is often more honest than the score itself, because it resists scale confusion — 84th percentile means the same thing whatever ruler the test used. The math is the cumulative normal distribution with mean 100 and the test's standard deviation; this page computes it exactly, from the same tested code that scores our free IQ test.
Remember that every real score carries measurement error — typically ±3–5 points on a clinical test and more online — so a percentile is really a percentile range. A reported 120 (91st percentile) is honestly "somewhere between the 84th and 95th". Every whole score also has its own page — for instance what an IQ of 120 means — and the full picture is on the IQ chart.
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Frequently Asked Questions
How do I convert an IQ score to a percentile?
Compute how many standard deviations the score sits from the mean — z = (IQ − 100) / 15 on the standard scale — then look up that z in the normal distribution. An IQ of 115 is z = 1, the 84th percentile; 130 is z = 2, the 98th. This calculator does the lookup exactly rather than from a rounded table.
Why does the test scale (SD 15 vs 16 vs 24) matter?
Because the same printed number means different rarities on different rulers. Modern Wechsler and Stanford–Binet tests use SD 15, the older Stanford–Binet used 16, and the Cattell scale used 24 — so "IQ 148" is 1-in-1,400 on SD 15 but only 1-in-40 on SD 24. Historical and society-reported scores are the usual place this bites.
What percentile is an IQ of 130?
The 97.7th percentile on the standard SD-15 scale — about 1 person in 44 scores at or above it, which is why 130 is the usual gifted-program threshold and high-IQ societies set entry near it (top 2%).