Average IQ by age
The average IQ is 100 at every age, because IQ tests compare people only with others their own age. What changes is underneath: processing speed peaks in the late teens, fluid reasoning in the mid-20s, and knowledge keeps growing for decades.
What's your IQ?
25 questions · about 12 minutes
What would you score? Try question 1.
Which option completes the grid? One tap, no sign-up.
IQ by age group
| Age group | Fluid reasoning | Knowledge | Average IQ |
|---|---|---|---|
| Children5 to 12 years | Developing fast | Building foundations | 100 |
| Teenagers13 to 17 years | Nearing its peak | Growing quickly | 100 |
| Adults18 to 65 years | Peaks mid-20s, then slow decline | Grows into the 60s | 100 |
| 65 and over65+ years | Declines more clearly | Often stable into the 70s and 80s | 100 |
Average IQ is 100 in every group because each age is scored against its own norms. For people over 65 that means age norms such as the WAIS-IV's, which run to age 90.
How does IQ change with age?
Average IQ by age follows a well-documented pattern. Cognitive abilities develop rapidly in childhood, fluid intelligence peaks in the mid-20s, crystallised intelligence grows through middle age, and processing speed, which peaks in the late teens, slows gradually from there. See at what age IQ is highest for the peak age of each ability.
None of this moves the average. When a test is built, the publisher tests a large sample at each age and sets the middle of every age group to 100, with a standard deviation of 15. A 10-year-old and a 60-year-old who both score 100 are both exactly typical for their age, even though they would solve different problems in different ways.
Each age group has its own page with an age-by-age table, the tests used and the questions people ask most: children, teenagers, adults and over 65.
Average IQ and IQ tests, age by age
The average does not change with age, so these pages are for the rest of the question: how the test works at each age, and what a score means there. Each age group has two kinds of page. The average IQ pages above give the statistics. The matching IQ test page covers how the LifeScore test works for that age. Two tools sit across both: the average IQ by age calculator and the mental age calculator.
- IQ test for kids and childrenParent guide for ages 8 to 12 and under
- IQ test for 8 year oldsAverage IQ at 8 is 100
- IQ test for 9 year oldsAverage IQ at 9 is 100
- IQ test for 10 year oldsAverage IQ at 10 is 100
- IQ test for 11 year oldsAverage IQ at 11 is 100
- IQ test for 12 year oldsAverage IQ at 12 is 100
- IQ test for teens and teenagersAges 13 to 17
- IQ test for 13 year oldsAverage IQ at 13 is 100
- IQ test for 14 year oldsAverage IQ at 14 is 100
- IQ test for 15 year oldsAverage IQ at 15 is 100
- IQ test for 16 year oldsAverage IQ at 16 is 100
- IQ test for 17 year oldsAverage IQ at 17 is 100
- IQ test for adultsThe standard adult test
- IQ test for over 40s
- IQ test for over 50s
- IQ test for seniorsAdults 60 and over
What's your IQ?
The test looks at pattern reasoning, the ability that peaks earliest. 25 visual reasoning questions.
25 questions · about 12 minutes
IQ scores are statistical measures of cognitive ability relative to age-matched peers. They are influenced by education, health, motivation and testing conditions, and a single score should not be the sole basis for important decisions. This page is for education and is not a substitute for professional psychological assessment. Last reviewed February 2026.