The IQ scale
IQ scores sit on a bell curve. Most people score near the middle, at 100, and fewer and fewer score further out on either side.
The share of people in each IQ range. The dashed line is the average, 100.
IQ ranges
The scale has a mean of 100 and a standard deviation of 15 (Neisser et al., 1996). That fixes how many people fall in each range.
Under 70
Lower end · 1st to 2nd percentile
2.3%
about 1 in 44
70 to 84
Lower range · 2nd to 14th percentile
14%
about 1 in 7
85 to 114
Average range · 16th to 82nd percentile
68%
about 7 in 10
115 to 129
Upper range · 84th to 97th percentile
14%
about 1 in 7
130 to 144
High range · 98th to 99th percentile
2.1%
about 1 in 47
145 and above
Top end · 99th percentile
0.1%
about 1 in 741
How to read the curve
68% of people score between 85 and 115, one standard deviation either side of 100. 95% score between 70 and 130.
The curve is symmetric: as many people score 10 points under 100 as 10 points over it. That is why an IQ of 100 is the 50th percentile, and why each 15 points away from the middle covers fewer people than the 15 before it.
Your own score as a percentile, or the other way round: IQ percentile calculator. How the test turns answers into a score: how we score.
What is a good IQ score?
100 is exactly the middle. Any score in the average range, 85 to 114, is where most people are. A score of 115 is higher than 84 of every 100 people, and 130 is higher than 98.
Why the average is 100, and how it has moved over the last century: average IQ.