Average IQ in the US: What the Numbers Really Mean

Why the US average is about 100

The WAIS, WISC and Stanford–Binet are standardised on thousands of Americans chosen to match census data on age, sex, race, region and education. By design, the US average on these tests is 100. When researchers compare countries on a UK-based scale, the US typically lands at 97 to 99 — a gap too small to mean much.

The Flynn effect in America

James Flynn documented that Americans gained around three IQ points per decade through much of the twentieth century. Test publishers re-norm regularly to keep the mean at 100. Some recent studies suggest the gains have slowed or reversed in certain areas, such as vocabulary and spatial reasoning, since the 2000s.

Variation by state and education

There is no official state-level IQ testing. Rankings that circulate online usually come from proxies such as NAEP school assessment scores, which reflect educational spending and poverty rates as much as ability. Education level is a stronger marker: average scores rise with each stage of schooling.

Mensa, the SAT and US testing culture

American Mensa admits people who score in the top 2% on an approved test, and historically accepted older SAT scores as qualifying evidence. SAT results correlate strongly with IQ but are also influenced by coaching and school quality.

Compare the US with other places in our guides to average IQ in the UK and average IQ by country, or take our free test to see your own estimate.

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