IQ Percentile Chart - Score to Percentile Conversion

What does an IQ percentile mean?

A percentile rank tells you what fraction of the population scores at or below your level. If your IQ is at the 98th percentile, 98 out of every 100 people score lower than you. If your IQ is at the 50th percentile, you scored higher than half the population and lower than half.

For most practical purposes, the percentile is more informative than the raw IQ number. "I am in the top 5%" communicates rarity directly; "I have an IQ of 125" requires the listener to know the conversion. The chart below gives you both.

IQ to percentile conversion table

Based on a normal distribution with mean 100 and standard deviation 15. Use this to look up your percentile from a measured IQ score:

How the conversion works

The conversion uses the cumulative standard normal distribution. The formula:

percentile = Φ((IQ − 100) / 15) × 100

Where Φ is the standard normal CDF. So for an IQ of 130: (130 − 100) / 15 = 2 standard deviations above the mean, and Φ(2) ≈ 0.977 = 97.7th percentile.

This assumes IQ is normally distributed, which is approximately true for the bulk of the population (roughly IQ 70 to 130) by construction of the test. The extreme tails (above 145 or below 55) deviate from true normality because (a) the calibration samples contain very few people there, and (b) some real-world distributions of cognitive ability have slightly fatter tails than the normal.

Common percentile reference points

• 50th percentile = IQ 100. The median.
• 84th percentile = IQ 115. One standard deviation above mean. Often the cutoff for university programs.
• 95th percentile = IQ 125. Top 5% of the population.
• 98th percentile = IQ 130. Mensa eligibility threshold.
• 99th percentile = IQ 135. Triple Nine Society territory (top 0.1% needs IQ 146+).
• 99.9th percentile = IQ 146. About 1 in 1,000 people.
• 99.99th percentile = IQ 156. About 1 in 10,000. Reliable measurement at this level requires specialized high-ceiling tests.

How accurate is percentile measurement?

Percentile accuracy depends on where you sit on the distribution:

• Between IQ 80 and 120 (about 80% of people): percentiles are well-calibrated. A measured IQ of 110 reliably corresponds to roughly the 75th percentile.
• Above IQ 130: calibration becomes shakier. Most IQ tests are standardized on samples of 1,500 to 2,200 people. The tail beyond 130 contains only 30 to 50 people in such samples - not enough to pin down exactly how rare an IQ of 145 vs 150 vs 155 actually is.
• Above IQ 160: percentile claims are largely theoretical. The Stanford-Binet 5 ceiling is 225 but scores above 160 are extrapolated, not measured. Claims of IQ 180+ should be treated with extreme skepticism.

Why your percentile matters more than your IQ

If a friend tells you their IQ is 120, you need to remember the scale and do the conversion. If they tell you "I am in the top 10%," you understand immediately what they mean. Percentiles are the unit most people actually need.

They also correctly communicate that small IQ differences at the tail are huge in rarity terms. The gap between IQ 130 and IQ 145 is only 15 points, but it is the difference between 1-in-44 and 1-in-741 - almost 17 times rarer.