What an IQ of 128 means
An IQ of 128 is higher than about 96.9% of people: roughly 1 in 32 score 128 or more. It is in the high range, 1.87 standard deviations above the average of 100.
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 128 good?
Yes, it is well above average: higher than about 96.9% of people.
What percentile is an IQ of 128?
An IQ of 128 is at the 96th percentile: it is higher than 96.9% 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 130 on a 16-point scale such as older Stanford-Binet editions, and about 145 on the 24-point Cattell scale.
How rare is an IQ of 128?
About 1 in 32 people score 128 or higher. In a group of 1,000 people, about 31 would be expected to score that high or higher.
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 | 119 to 137 |
| A test with reliability 0.90 | ±8 | 120 to 136 |
| A test with reliability 0.95 | ±6 | 122 to 134 |
The margin is 1.645 standard errors of measurement, which covers about 90% of retakes.
What an IQ of 128 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.