The average IQ is 100. That is not a discovery — it is how IQ tests are built. Once you understand that rule, you can read any score, know what an IQ of 115 or 130 is worth, and see why the famous "average IQ by country" maps are far shakier than they look.
The average IQ is 100 — by design
An IQ test does not measure an absolute quantity the way a scale measures weight. It compares your answers with those of a large sample of people your age, known as the norming sample. Test makers then set the scale so that this sample's average lands exactly on 100, with a standard deviation (the usual spread around the average) of 15 points.
So the average IQ cannot "drop" or "rise" on a current test: it is reset to 100 every time the test is re-normed. What changes over the decades is how many questions people answer correctly, not the average that gets reported.
What 85, 100, 115 and 130 mean
IQ scores follow a bell curve. With an average of 100 and a standard deviation of 15, the proportions are always the same:
| IQ | Share of people | Meaning |
|---|---|---|
| below 70 | about 2.3% | well below average |
| 70 to 85 | about 13.6% | below average |
| 85 to 115 | about 68% | average range |
| 115 to 130 | about 13.6% | above average |
| above 130 | about 2.3% | well above average |
In other words, two people out of three score between 85 and 115. An IQ of 115 beats about 84% of people the same age; 120 beats about 91%; 130 beats about 98%. That top 2% is also the bar used by the high-IQ society Mensa, which admits people who score in the top 2% on an accepted test.
Remember that a score is never an exact point: even a test given by a psychologist has a margin of error of a few points. A 112 and a 117 say almost the same thing.
Average IQ by age
Because everyone is compared with people of their own age, the average IQ is 100 at 20 and at 70. A "normal IQ by age" chart that declines over the years does not exist on serious tests.
What does change are the abilities themselves. Long-term studies show that some decline early, such as processing speed and solving new problems, starting in early adulthood. Others, such as vocabulary and general knowledge, often keep growing until late in life. The psychologist Timothy Salthouse summed up this double movement in 2009. It is exactly why tests are normed by age group.
Average IQ for women and men
The research answer is short: on a full IQ test, women's and men's averages are practically the same. The landmark 1996 report commissioned by the American Psychological Association, led by Ulric Neisser, already said so. Differences exist on some individual subtests, in both directions, but they tell you nothing about any one person.
Average IQ by country: why the rankings mislead
The world maps that assign an "average IQ" to every country come mostly from a few old compilations. They lump together very different studies: small samples, sometimes only schoolchildren, a mix of tests and outdated norms. A 2010 systematic review by Jelte Wicherts and colleagues showed that, for sub-Saharan Africa, those compilations used figures well below what the strongest studies report.
Two facts call for caution:
- Each test is normed on its own country's population. A test normed in the United States gives Americans an average of 100 by definition — and the same is true in the UK, Germany or Brazil on their own norms.
- Raw scores depend on the environment. In 1987, the researcher James Flynn showed that raw scores had risen by about 3 points per decade in the countries studied during the 20th century — the "Flynn effect". Gains that fast cannot come from genes: they reflect schooling, health, nutrition and familiarity with this kind of task.
Comparing countries with different tests and living conditions mostly compares schools, health systems and eras — not brains.
How to find out your IQ
Only a psychologist using a normed test such as the WAIS (Wechsler Adult Intelligence Scale) can establish a clinical IQ, over several hours and many subtests. Online tests give an estimate: useful to see where you stand, to practise, or to decide whether to go further — as long as you do not take them for a diagnosis.
🧩Test yourselfIQ test26 logic puzzles, an estimated score · test in FrenchStart →Our IQ test is built on logic puzzles (number series and matrices, no general-knowledge questions) and gives an estimated score with its margin of uncertainty. You can also warm up for free with a visual logic test.
🧩Test yourself · freeLogic test20 visual puzzles · test in FrenchStart →IQ is not everything
IQ predicts school results fairly well — the 1996 report put its correlation with grades at about 0.5, a real link but far from the whole story. Motivation, organisation, curiosity, health and support matter at least as much in a life. An IQ score is a snapshot of some reasoning skills on a given day — not a label, and not a destiny.
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Frequently asked questions
What is the average IQ score?
100. Every IQ test is normed so that the average of its reference population is exactly 100, with a standard deviation of 15.
Is an IQ of 120 good?
Yes, it is above average: an IQ of 120 beats roughly 91% of people the same age.
What IQ counts as gifted?
A score of 130 or more is the most common threshold — roughly the top 2% of the population.
Can your IQ change over time?
It is fairly stable in adulthood but not fixed: scores vary by a few points between sittings, and schooling, health or practice with this type of task can shift them.
Sources
- Neisser U. et al. (1996). Intelligence: Knowns and unknowns. American Psychologist, 51(2), 77–101. — doi.org/10.1037/0003-066X.51.2.77
- 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
- Wicherts J. M., Dolan C. V., 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
- Salthouse T. A. (2009). When does age-related cognitive decline begin? Neurobiology of Aging, 30(4), 507–514. — doi.org/10.1016/j.neurobiolaging.2008.09.023
The MyMindTests team writes about the brain from published studies. Every figure is sourced and checked before publication.