What an IQ of 100 means
An IQ of 100 is exactly average. Half of people score higher and half score lower, and it sits in the middle of the average range, 90 to 109.
The amber band is the likely range on a retake of our test, 9 points either side. The curve is the normal distribution with a mean of 100 and a standard deviation of 15.
Is an IQ of 100 good?
It is an average score, the most common result there is. About 49% of people score between 90 and 109.
What percentile is an IQ of 100?
An IQ of 100 is at the 50th percentile: it is higher than 50.0% of people on a scale with a mean of 100 and a standard deviation of 15.
Tests that use a different standard deviation give the same rarity a different number: about 100 on a 16-point scale such as older Stanford-Binet editions, and about 100 on the 24-point Cattell scale.
How rare is an IQ of 100?
It is the most common score of all. About half of people score above 100 and half below, and about two in three score within 15 points of it.
How much could a retake change it?
No test gives the same score twice. The likely range is where about 90 in 100 retakes would land, and its width depends on how reliable the test is.1
| Test | Margin of error | Likely range |
|---|---|---|
| Our test (reliability 0.87) | ±9 | 91 to 109 |
| A test with reliability 0.90 | ±8 | 92 to 108 |
| A test with reliability 0.95 | ±6 | 94 to 106 |
The margin is 1.645 standard errors of measurement, which covers about 90% of retakes.
What an IQ of 100 does not tell you
A score describes how someone did on one set of reasoning tasks on one day. It does not measure what a person knows, how hard they work or what they will achieve.
An online test is for interest. For a score that counts for school, work or health, a psychologist can give a full assessment in person.
Nearby scores
Sources
- American Educational Research Association, American Psychological Association and National Council on Measurement in Education (2014). Standards for Educational and Psychological Testing, chapter 2: Reliability/Precision and Errors of Measurement. www.testingstandards.net/open-access-files.html
First published 13 November 2026.