The IQ scale, explained properly

IQ scores are a relative scale: 100 is defined as the average of your age group, and 15 points — one standard deviation — is the unit everything else hangs on. Here is the whole scale, what each range means, and the percentile behind every score.

2%14%34%34%14%2%557085100115130145mean 100 · each band of 15 points = one standard deviation

IQ score ranges and labels

These are the Wechsler-style labels most reports use. Treat them as mile markers, not verdicts — two attempts by the same person routinely differ by several points, which is why our test reports a range rather than a single number.

RangeLabelHow common
130+Very superiorabout 1 person in 44
120–129Superiorabout 9% of people
110–119High averageabout 16% of people
90–109Averageabout half of everyone
80–89Low averageabout 16% of people
70–79Borderlineabout 7% of people
below 70Clinical assessment rangeabout 2% — a matter for professionals, not websites

Percentiles for common scores

IQPercentileMeaning
8516%below the mean
10050%dead average — by definition
11075%above the mean
11584%above the mean
12091%above the mean
12595%above the mean
13098%high-IQ-society territory
13599.0%high-IQ-society territory
14099.6%high-IQ-society territory
14599.9%high-IQ-society territory

Every whole score from 70 to 160 has its own page — e.g. what an IQ of 127 means — or convert any score with the IQ percentile calculator.

What is the IQ scale range?

Modern IQ tests are scaled so the mean is 100 and the standard deviation 15. Nearly everyone (99.7%) scores between 55 and 145; about 68% score between 85 and 115. Scores outside 55–145 are quoted sometimes, but no ordinary test measures reliably out there — specialised instruments and very large caveats apply.

Is the IQ scale the same on every test?

The scale is; the scores are not automatically. Wechsler tests and modern Stanford–Binet both use mean 100, SD 15, so their numbers are comparable. Some older tests and some online tests use SD 16 or even 24 — a "160" on an SD-24 scale is a 137.5 on the standard one. Always check the SD before comparing scores.

What does a standard deviation mean here?

It is the scale’s ruler. One SD (15 points) either side of 100 covers the middle two-thirds of people. Two SDs (70–130) covers 95%. Each further SD gets exponentially rarer — which is why a 145 (1 in ~740) is a different universe from a 130 (1 in ~44), despite being "only" 15 points apart.

Does the IQ scale change with age?

The scale stays put — 100 is always the average for your age group. What changes is the raw performance needed to hit it: fluid reasoning peaks in the twenties and drifts down while vocabulary holds, so tests re-anchor the scale within each age band. That is also why an online test that ignores your age can’t place you precisely.

Where do you land on this scale? Free, untimed, no email — the result appears instantly as an honest range.

Take the free IQ test