Understanding the curve
IQ scores are scaled so the population forms a bell curve with a mean of 100 and a standard deviation of 15. That shape is what makes a percentile ranking meaningful: most people cluster near the middle, and scores become rarer — and more informative — the further they sit from the average.
Drag the slider to place any score on the population curve and see the percentile it corresponds to.
IQ score
100
Percentile
50
Classification
Average
An IQ of 100 sits at about the 50th percentile — roughly 1 in 2 people score at or above this level, or about 50% of the population.
Percentiles and population shares below are derived from the same normal distribution (mean 100, SD 15).
| IQ range | Classification | Percentile band | Share of population |
|---|---|---|---|
| 130 and above | Very Superior | 97.7 and above | 0.0% |
| 120–129 | Superior | 90.9–97.3 | 0.1% |
| 110–119 | High Average | 74.8–89.7 | 0.2% |
| 90–109 | Average | 25.2–72.6 | 0.5% |
| 80–89 | Low Average | 9.1–23.2 | 0.2% |
| 70–79 | Borderline | 2.3–8.1 | 0.1% |
| Below 70 | Extremely Low | Below 2.3 | 0.0% |
A percentile tells you what share of the comparison population scored at or below a given score. Small differences near the middle of the curve (say 100 versus 105) cover a large slice of the population, while a few points near the extremes represent a much rarer group — which is why the same gap means different things in different parts of the curve.
Take the 30-question assessment to get your own IQ estimate, percentile ranking and domain-by-domain breakdown.
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