IQ scale
What an IQ score means
An IQ score tells you where you stand compared with other people, not how many questions you got right. Almost every modern test reports on the same scale: the average is set at 100 and the standard deviation at 15. That makes the number a position you can read straight off the curve below.
Score ranges
| Score | Label | Position | Share of people |
|---|---|---|---|
| 130 and above | Gifted | Top 2% | 2% |
| 120 to 129 | Superior | Top 10% | 7% |
| 110 to 119 | Above average | Top 25% | 16% |
| 90 to 109 | Average | Middle half | 50% |
| 80 to 89 | Low average | Bottom 25% | 16% |
| 70 to 79 | Borderline | Bottom 10% | 7% |
| Below 70 | Extremely low | Bottom 2% | 2% |
The share column comes from the shape of the normal distribution, not from counting the people who took this test. Any test reported on this scale has the same shares by construction: about half of everyone scores between 90 and 109, and about 2% score 130 or above.
Turn a score into a percentile
Type in a score from any test and pick the scale it was reported on.
84.1 percentile
Higher than about 84 in every 100 people. About 1 in 6 people score this high or higher.
Band: Above average
A percentile is not a percentage correct
A percentile of 75 means you scored higher than 75 out of every 100 people in the comparison group. It says nothing about how many questions you answered correctly. Two tests can give the same percentile for very different raw scores, because one is harder than the other.
Why two tests can disagree
Not every test uses a standard deviation of 15. The Cattell scales use 24, and older editions of the Stanford-Binet used 16. A Cattell score of 148 is the same position as 130 on most other tests: both are two standard deviations above the average. The calculator above converts between them.
Every score also carries some uncertainty. Take the same test twice and the number will move a few points, which is why this test reports a range alongside your score. It also reports nothing below 55 or above 145. Beyond about three standard deviations from the average, a 30-question test cannot reliably tell one score from the next.
What a band label is for
Labels such as "Superior" or "Borderline" are conventions for describing a position on the scale. Different publishers draw the lines in slightly different places, and none of the labels is a diagnosis. Clinical classifications depend on a full assessment by a qualified professional, never on a single score.