Average IQ by Age
ScoresLast updated: September 1, 2026
What is the average IQ for a 13 year old?
The average IQ for a 13 year old is about 100. IQ scores are age-normed, which means a 13 year old is compared only with other 13 year olds, not with adults. The same is true at every age, so the average score for any single age group is set at roughly 100 by design.
This is the part that trips people up. A search for "average IQ for a 13 year old" turns up tables of numbers that rise year by year, as if a 15 year old is expected to score higher than a 13 year old. That is a misreading of how the score works.
A 13 year old who scores 100 and a 40 year old who scores 100 have each done the same thing: matched the middle of their own age group. The score is a rank within an age band, not a running total that grows as you get older.
Does IQ increase with age?
Not as a standardized score. Raw ability on many tasks does grow through childhood and into early adulthood, but the score is re-centered on 100 for each age group, so that growth is normed out. A child's raw performance rises year to year while the age-adjusted score stays near 100.
Think of it like height percentiles on a growth chart. A child gets taller every year, but a child who tracks the 60th percentile at age 6 and again at age 10 has not "gained percentile". IQ norming does the same thing with reasoning tasks.
So both statements are true at once: a teenager can solve harder problems than they could at age 8, and their IQ score has barely moved. The test is measuring their position in the pack, and the pack grew with them.
Why is the average always around 100?
The average is always about 100 because 100 is defined as the midpoint of the reference group. Test makers collect scores from a large, age-stratified sample, then set the scale so the middle of each age group lands on 100, with a standard deviation of 15. Periodic re-norming keeps it there over the years.
The table below is built to teach this rather than to invent different averages. Every row shows about 100, because that is what age-norming produces. The real, measurable age differences live in the last column, in raw performance, which the norming process removes from the final number.
| Age group | Average age-normed IQ | What actually changes with age |
|---|---|---|
| 6 to 8 | About 100 | Raw scores climb fast; performance is compared only within this age band |
| 9 to 12 | About 100 | Raw reasoning and memory grow; norms adjust for it |
| 13 to 15 | About 100 | Large raw gains during adolescence, normed out of the score |
| 16 to 24 | About 100 | Raw processing speed and working memory near their peak |
| 25 to 44 | About 100 | Vocabulary and general knowledge still rising |
| 45 to 64 | About 100 | Raw processing speed slowly declines; knowledge holds |
| 65 and over | About 100 | Wider individual variation; norms adjusted for the age group |
The pattern in that last column is well established: speed-based abilities tend to peak early, and knowledge-based abilities tend to hold or keep growing for decades. None of that shows up in the headline IQ number, because the number is re-scaled for each age.
How stable are children's IQ scores?
Children's IQ scores are less stable than adult scores, and the younger the child, the less a single result predicts later scores. A score taken at age 5 can shift noticeably by age 12 as a child develops. Stability improves through middle childhood and is much stronger from about age 10 onward.
Two things drive the movement. One is ordinary measurement error, present at every age. The other is real developmental change: children mature at different rates, and a slow start or a fast start at age 5 does not lock in a trajectory.
How much of adult ability is settled in early childhood is still debated among researchers, and estimates of the link between an early score and an adult score vary widely between studies. The careful reading is that an early score is weak evidence about a teenager or an adult, and should not be treated as a ceiling or a promise.
Should parents test their child's IQ?
For most families there is no need. A formal IQ test is useful when a school or clinician recommends one to look into a specific concern, such as a suspected learning difference or a gifted-programme placement. Testing done purely out of curiosity produces a fragile number and can lead to labels that are hard to undo.
If a test does happen, a few principles help a parent read it responsibly:
- Treat any score as an estimate with error, not a fixed trait.
- Read the full report and the psychologist's interpretation, not one number in isolation.
- Do not hand the child the number as a label to live up to or down to.
- Remember the score misses motivation, creativity, persistence, and social skill, which matter as much for how a child does in school and life.
- Online tests, including the ones on this site, are not valid for children and are not a substitute for a professional assessment.
If an older child simply wants to try reasoning puzzles for fun, the free IQ-style test for kids here is built for that. It gives a rough score for entertainment only, not a measure a school or clinician would use.
Frequently Asked Questions
What is the average IQ for a 10 year old?
About 100, the same as for any age group. A 10 year old is scored against other 10 year olds, so the middle of that group is set at 100 by design.
Is a 120 IQ good for a 13 year old?
It is a high score, near the top 10 percent for that age group. As at any age, a score that close to the edge of a band could move a few points on another day.
Do people get smarter or less smart as they age?
Raw abilities follow different paths. Processing speed tends to peak young, while vocabulary and general knowledge often keep growing for decades. The age-normed IQ score is built to stay near 100 across the lifespan.
Why do some websites show IQ rising with age?
Those tables usually confuse raw performance with the standardized score. Raw scores do rise through childhood, but the IQ number is re-centered for each age group, so it does not climb with age.
At what age is an IQ score reliable?
Reliability improves through childhood. Scores from around age 10 predict later scores reasonably well. Results before school age are far more provisional and are often reported as developmental measures instead.
Where a score actually fits
An age-normed score answers one narrow question: how did this person do compared with others the same age, on this test, on this day. It does not measure worth, potential, or what someone will achieve. If you want to see the format for yourself, our free IQ test gives an instant estimate for adults, for curiosity rather than diagnosis.