IQ Percentile Chart: What Percentile Is Your IQ?

How percentile is calculated from the bell curve

The percentile comes straight from the position of your score on the normal distribution. Every IQ score is first turned into a z-score, which is the number of standard deviations it sits away from the average:

z = (your IQ − 100) ÷ 15

Then the percentile is the area of the bell curve to the left of that z-score. You do not have to do this by hand, but the logic is worth seeing once:

• IQ 115 gives z = (115 − 100) ÷ 15 = +1.0. One standard deviation above the mean covers 84.1% of the area, so IQ 115 is the 84th percentile.
• IQ 130 gives z = +2.0, which covers 97.7% of the area, so it is the 98th percentile.
• IQ 85 gives z = −1.0, which lands at the 15.9th percentile, the mirror image of 115.

This is also why the famous "68-95-99.7" rule applies to IQ. About 68% of people fall within one standard deviation of the mean (IQ 85 to 115), about 95% within two (IQ 70 to 130), and about 99.7% within three (IQ 55 to 145). The steepest part of the curve is in the middle, which is why a 5-point move near 100 changes your percentile far more than a 5-point move out at 140.

What the 98th and 99th percentile mean

The 98th percentile is the number people ask about most, because it is Mensa's cutoff. Mensa admits scores at or above the 98th percentile on an approved, supervised test, which is the top 1 in 50. On the Wechsler scale (SD 15) that threshold is an IQ of 130. On the Stanford-Binet 5 (SD 16) the same percentile is 132, and on the Cattell III B (SD 24) used by British Mensa it is 148. The percentile is identical across all three; only the scale label changes, because each test spreads its scores with a different standard deviation.

The 99th percentile sits a little higher, around IQ 135 on the SD-15 scale, where roughly 1 person in 100 scores at or above you. Past that, the numbers thin out fast: the 99.9th percentile is about IQ 145, or 1 in 741. This is the key thing to understand about the top end. Because the bell curve tapers, huge jumps in rarity come from small jumps in score. Going from IQ 130 to 145 is only 15 points, but it moves you from 1 in 44 to about 1 in 741.

One honest caveat: at the extreme high end, percentile figures depend heavily on the quality of the test's norming sample, and a casual online test cannot reliably distinguish, say, the 99.9th from the 99.99th percentile. Treat percentiles above roughly 99.5 as approximate.

How to read your own percentile

Start with your score, find the nearest row in the chart, and read across. A few practical rules keep you from misreading it:

1. Percentile is a rank, not a grade. The 84th percentile does not mean you got 84% of questions right. It means you outranked 84% of people.
2. Always check the scale. A percentile is only meaningful next to its standard deviation. IQ 132 sounds higher than 130, but on the Stanford-Binet's SD-16 scale it is the exact same 98th percentile as a Wechsler 130.
3. The middle is crowded. Because most people cluster near 100, scores of 95, 100, and 105 are separated by more percentile points than they feel. All three are squarely "average."
4. Percentiles are population-relative. Your percentile answers "compared to everyone," not "compared to my class or my field." Among a group that is already selected for high ability, the same score sits at a lower internal percentile.

Our own test at iq-test-official.site scores on this same standard scale (mean 100, SD 15) and returns your percentile alongside the raw number, so you can see your rank rather than guess it. The test is free to take; unlocking your full detailed result is a one-time paid report, with no subscription and no automatic renewal.

FAQ

Q: What percentile is an IQ of 120?

A: IQ 120 is the 91st percentile. You scored higher than about 91% of people, and roughly 1 person in 11 scores at or above 120 on the SD-15 scale. It falls in the "superior" band, comfortably above average but below the gifted range.

Q: What IQ is the 98th percentile?

A: The 98th percentile is an IQ of 130 on the Wechsler scale. That is two standard deviations above the average of 100 and the standard cutoff for Mensa. The same percentile equals 132 on the Stanford-Binet and 148 on the Cattell scale, because each uses a different standard deviation.

Q: How do I convert my IQ score to a percentile?

A: Calculate z = (your IQ − 100) ÷ 15, then look up the area to the left of that z-score. For example, IQ 125 gives z = 1.67, which corresponds to the 95th percentile. The chart above does this conversion for you at every 5-point step from 70 to 145.

Q: Is the 99th percentile a good IQ score?

A: Yes, the 99th percentile is roughly IQ 135, placing you in the top 1% of the population. Only about 1 person in 100 scores at or above it. It sits above Mensa's 98th-percentile threshold and is well into the very gifted range.

References

• Wechsler, D. (2008). Wechsler Adult Intelligence Scale — Fourth Edition (WAIS-IV): Technical and Interpretive Manual. Pearson. (Mean 100, SD 15 scaling and percentile norms.)
• Mensa International. Qualifying test scores. https://www.mensa.org/join/testscores/qualifying-test-scores
• American Psychological Association. APA Dictionary of Psychology: percentile and normal distribution. https://dictionary.apa.org/percentile

Last updated: July 13, 2026