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What is the average IQ?

The average IQ is 100. Tests are scored so that the middle of the population lands on 100, and about 68% of people score between 85 and 115.

Figure 1. Where people score around the average

The curve is the normal distribution with a mean of 100 and a standard deviation of 15. Gridlines mark each standard deviation from the average.

Why is the average IQ 100?

Because tests are built that way. When a test is made, it is given to a large norm group chosen to match the population, and the average score of that group is set to 100. The spread is set so that one standard deviation is 15 points on most tests.

So 100 is not a measured fact about people. It is the point the scale is anchored to, and every other score says how far someone is from it.1

What is a normal IQ range?

The usual answer is 85 to 115, one standard deviation either side of 100, where about 68% of people score. About 95% score between 70 and 130.

Our own level names call 90 to 109 average, 110 to 119 high average and 80 to 89 low average. All of these are common results.

Table 1. How many people score near the average
RangeDistance from 100Share of people
85 to 1151 standard deviation either side68.3%
70 to 1302 standard deviations either side95.4%
55 to 1453 standard deviations either side99.7%

Shares come from the bell curve for a scale with a mean of 100 and a standard deviation of 15.

What is the average IQ by age?

It is 100 at every age. A child is compared with children of the same age, and an adult with adults in the same age band, so the middle of each group scores 100.

A ten-year-old who scores 100 and an adult who scores 100 have not answered the same number of questions right. Each is in the middle of their own group. That is why an IQ score stays fairly steady through life even though raw ability changes.1

Table 2. Average IQ by age
AgeAverage IQCompared with
Children100Children of the same age
Teenagers100Teenagers of the same age
Adults100Adults in the same age band
Older adults100Older adults in the same age band

Raw scores change with age, but each person is scored against their own age group, so the average stays 100.

What is the average IQ in the US?

It is 100 on tests whose norm groups are drawn from the US population, which includes the most widely used tests. The average score of the norm group is defined as 100, so the US average is 100 by construction.

Figures that give a different US average usually come from a different test, an older norm group or a sample that does not represent the country.2

What about the average IQ by country?

League tables of national IQ circulate widely. They mix different tests, years and age groups, and many of the samples behind them were small or not representative of the country.

A systematic review of the studies behind one region's figures found many samples unsuitable and arrived at a different average from the best-known table. We do not publish a country table. If we ever do, it will come from our own results, with its limits stated.3

Has the average IQ changed over time?

Yes. Through the twentieth century, people in many countries scored higher on the same tests than earlier generations did. This rise is called the Flynn effect.

Because of it, tests are re-normed every so often, so that the average of the new norm group is set back to 100.4

Sources

  1. Neisser, U., et al. (1996). Intelligence: Knowns and unknowns. American Psychologist, 51(2), 77–101. doi.org/10.1037/0003-066X.51.2.77
  2. Mensa International. What is IQ? (read 13 November 2026). www.mensa.org/what-is-iq/
  3. Wicherts, J. M., Dolan, C. V., and van der Maas, H. L. J. (2010). A systematic literature review of the average IQ of sub-Saharan Africans. Intelligence, 38(1), 1–20. doi.org/10.1016/j.intell.2009.05.002
  4. Flynn, J. R. (1987). Massive IQ gains in 14 nations: What IQ tests really measure. Psychological Bulletin, 101(2), 171–191. doi.org/10.1037/0033-2909.101.2.171

First published 13 November 2026.