Quick answer: the average IQ is 100, by design. About two in three people (68%) score between 85 and 115, about 95% between 70 and 130, and only about 2% score 130 or more.
Find your own score: take the free IQ test
Why the average IQ is always 100
An IQ score is not a count of right answers. It says where you sit compared with a reference group. Test makers set the scale so that the middle score of that group is 100 and the spread, called the standard deviation, is 15 (a few older tests use 16). Because the scale is built that way, 100 is the average by definition, and the share of people at each score follows a bell curve.
IQ score to percentile
Your percentile is the share of people who would score lower than you. These follow directly from the standard scale (average 100, standard deviation 15).
| IQ score | Percentile | How common |
|---|---|---|
| 70 | 2nd | about 1 in 44 score at or below this |
| 85 | 16th | about 1 in 6 score at or below this |
| 100 | 50th | the middle: half score higher, half lower |
| 115 | 84th | about 1 in 6 score at or above this |
| 120 | 91st | about 1 in 11 score at or above this |
| 130 | 98th | about 1 in 44 score at or above this |
| 145 | 99.9th | about 1 in 741 score at or above this |
For a labelled chart of what each range is called, see the IQ score chart on our IQ test page.
Average IQ by age
The average IQ is 100 at every age, because your score is compared with people of your own age. A 10-year-old and a 70-year-old who both score 100 are both exactly average for their age group, even though their raw puzzle performance is different.
What does change with age is raw performance on particular skills. A large study of cognitive tests found no single age at which everything peaks: Hartshorne and Germine (2015) report that some abilities, such as processing speed, peak around the end of school, some plateau in early adulthood and begin to decline in the 30s, and others, such as vocabulary and general knowledge, keep improving much later. That is why “average IQ by age” has no table of different averages: the scale is deliberately reset for each age group.
Is the average IQ going up or down?
Raw test scores rose by about 3 points a decade through the 20th century, a trend called the Flynn effect. In several Western countries the rise has since slowed or reversed. The clearest evidence is a study of 730,000 Norwegian military conscripts: Bratsberg and Rogeberg (2018) found scores peaked for men born in the mid-1970s and fell afterwards, and that the pattern showed up within families, which points to environmental causes rather than genes. Test publishers re-scale their tests from time to time so that the average stays at 100.
We don’t publish a table of average IQ by country. The figures that circulate online mix different tests and different kinds of sample, so they are not comparable.
What Altto test takers score
These are finished Altto IQ tests up to 9 November 2026, with no names or personal details involved. Altto’s test is an unofficial practice test and the people who take it chose to, so this is not a measure of the UK’s average. It is simply how our test takers compare with the textbook curve.
| Test | Finished tests | Average score | Under 85 | 85–114 | 115–129 | 130+ |
|---|---|---|---|---|---|---|
| Standard (20 questions) | 1,420 | 101.8 | 12.7% | 66.8% | 16.5% | 4.0% |
| Quick (10 questions) | 467 | 103.2 | 15.4% | 58.7% | 18.0% | 7.9% |
| Complete (40 questions) | 233 | 110.3 | 4.3% | 52.8% | 34.3% | 8.6% |
| Expected for the whole population | – | 100.0 | 15.9% | 68.3% | 13.6% | 2.3% |
Altto’s standard test lands close to the textbook figures, with slightly fewer low scores and slightly more high ones. That is what you would expect from people who pick an IQ test for fun. The longer 40-question test averages higher still; it is likely taken by people who are keener on puzzles. Treat all of this as a description of our visitors, not of the population.
Are online IQ tests accurate?
No online test, free or paid, gives an official IQ score. Only a supervised test given by a psychologist, or Mensa’s supervised test, does that. An online test gives an estimate, and the result can move by several points if you retake it. Shorter tests are less precise than longer ones. See our guide to which online IQ tests are actually free.
Find out where you stand
Altto’s IQ test has 10, 20 or 40 puzzles covering patterns, numbers, shapes and logic. Your score, percentile, ability profile and every answer explained appear the moment you finish, with a free certificate if you want one. No sign-up, no email and no card.
Take the free IQ testMore free tests: brain age, reaction time, typing speed and personality, all on the tests page.
Frequently asked questions
What is the average IQ?
100. IQ tests are scaled so that the middle score of the group they were standardised on is 100, with a standard deviation of 15. About two in three people score between 85 and 115, and about 95% score between 70 and 130.
What is the average IQ of an adult?
Also 100. Scores are compared with people of the same age, so the average is 100 for children, adults and older people alike. It does not fall as you get older.
What is a good IQ score?
Anything from 90 to 109 is average, 110 to 119 is high average, and 120 or more is well above average (about 1 in 11 people). Scores are estimates, so a few points either way is normal. A single online test is not a diagnosis.
Is the average IQ in the UK different from 100?
Not by definition: tests are scaled so the reference population averages 100, so there is no separate UK figure to look up. Country averages published online mix different tests and samples, so we don't rank countries.
Is the average IQ going up or down?
Raw scores rose by about 3 points a decade through the 20th century (the Flynn effect). In several Western countries the rise has slowed or reversed in recent decades; the clearest evidence is from Norwegian military conscripts born after the mid-1970s. Tests are re-scaled from time to time so that the average stays at 100.
Is Altto's IQ test an official IQ test?
No. It is a free practice test that gives an estimate, scored in your browser. Only a supervised test from a psychologist (or Mensa's supervised test) gives an official score.