The average IQ score is 100.That isn't a coincidence or a survey result — it's how IQ tests are built. Every major test is standardized so that the mean score of the population is exactly 100, with a standard deviation of 15 points. About 68% of people score between 85 and 115, and roughly 95% score between 70 and 130.
Why the average is always 100
When a new IQ test is developed (or an old one revised), it is given to a large, representative sample of people — the norming sample. Raw results are then mapped onto a bell curve centered at 100. Your IQ score is therefore not a count of correct answers; it's a statement about where you stand relative to everyone else. A score of 115 means you scored one standard deviation above the mean — higher than about 84% of the population.
How IQ scores are distributed
| IQ range | Share of population | Description |
|---|---|---|
| 130 and above | ~2.1% | Very superior / gifted |
| 120–129 | ~6.4% | Superior |
| 110–119 | ~15.7% | High average |
| 90–109 | ~50% | Average |
| 80–89 | ~15.7% | Low average |
| 70–79 | ~6.4% | Borderline |
| Below 70 | ~2.1% | Extremely low |
For a deeper breakdown of each range, see our guides to the IQ scale and the IQ score chart, or convert any score to a population rank with the IQ percentile table.
Average IQ by age
Because scores are age-normed, the average is 100 at every age: a 25-year-old and a 70-year-old are each compared to their own age group. Underneath the norming, raw abilities do change — fluid reasoning (solving novel problems) typically peaks in the 20s and gradually declines, while crystallized knowledge (vocabulary, facts, skills) keeps growing into the 60s. We cover this in detail in average IQ by age.
Average IQ by country — read with caution
You'll find many tables online claiming national average IQs. The honest summary: measured averages differ between countries, but the differences track education access, childhood nutrition, health care and test familiarity — and many national estimates are built on small or unrepresentative samples. Country rankings make good clickbait and poor science.
The Flynn effect: averages have been rising
Raw performance on IQ tests rose steadily through the 20th century — about 3 points per decade — a phenomenon named the Flynn effect after researcher James Flynn. Better schooling, nutrition, smaller families and a more abstraction-heavy world are the leading explanations. Because tests are re-normed, the published average stays at 100 even as raw performance shifts; some wealthy countries now show a plateau or slight reversal.
What "average" means for you
A single number can't capture a mind. Two people with identical IQ 100 scores can have very different cognitive profiles — one strong in working memory, the other in visual-spatial reasoning. That's why a useful assessment reports how you think, not just a number: your percentile, your strengths across abilities, and where focused training will move the needle.