Is an IQ of 100 average?
Yes. An IQ of 100 is in the average range, at or just above the exact middle of the population. You score at least as high as about half of people your age, a solid result for school, work and everyday life.
Where 100 sits on the bell curve
An IQ of 100 is exactly the average. It is higher than about 50% of people of the same age, shown by the shaded area below. This is the peak of the bell curve, where more people score than anywhere else.
On other IQ scales, the same result would be about 100 on a test with a standard deviation of 16, such as older editions of the Stanford-Binet, and 100 on the Cattell scale, which uses 24. Why scales differ.
IQ 100 meaning: a closer look
An IQ of 100 is the exact middle of the scale by design: test makers set the average of each age group to 100. Half of people score higher and half lower. A common mix-up is that 100 means you got every question right, or 100% correct. It doesn't. It means your performance matched the typical person of your age in the test's comparison group. A score of 100 is exactly average, the most common area of the whole bell curve, and a perfectly good result for school, work and everyday life.
Why 100 is the average: Wechsler's 1939 deviation IQ
Early IQs were ratios designed for children, and they behaved oddly. David Wechsler pointed out that on Terman and Merrill's revised Stanford-Binet, the spread of IQs changed with age: the standard deviation was 20.0 at age 12 but only 12.5 at age 6, so the same relative standing could produce different IQs at different ages. In his Wechsler-Bellevue scale of 1939, he instead compared each person with others of the same age. In his own account, the mean stayed at 100 because "the historical definition has set it once and for all at 100".
The spread came from a practical choice. Wechsler placed an IQ of 90, the usual lower edge of average, one "probable error" below the mean. A probable error is about two thirds of a standard deviation, which works out at roughly 15 IQ points per standard deviation, the convention still used today. In his 1944 edition, scores from 1,508 people aged 10 to 60 had a mean of 100.11 and a standard deviation of 14.69. Every IQ of 100 since then marks the same thing: the middle of the person's own age group.
Sources: Wechsler (1944), The Measurement of Adult Intelligence, 3rd edition (first edition 1939), Williams and Wilkins; Boake (2002), "From the Binet-Simon to the Wechsler-Bellevue: tracing the history of intelligence testing", Journal of Clinical and Experimental Neuropsychology, 24(3).
What 100 looks like among real people
If you lined up 100 people of your age, about 50 would score lower than 100 and about 50 would score the same or higher. The orange dot marks your place in the line.
A score here puts you in the middle of almost any group: about as many people score above you as below.
How precise is a score of 100?
No IQ test measures to the exact point. On a professional test, a result of 100 usually comes with a likely range of about five points either way: 95 to 105. That range runs from the 37th to the 63rd percentile, all within the average range.
Because this is the most crowded part of the scale, a retest could easily move you a few places either side of the middle without anything having changed.
On the Assessivo test, 100 is the score for 18 correct answers out of 36. How our score is worked out.
So if you scored 100 once, a retest on another day could reasonably land anywhere from 95 to 105. Online tests are less precise still, so treat any online result as a rough estimate.
IQ 100 and mental age in children
Early IQ tests for children worked with a "mental age", the age whose typical performance a child matched. The IQ was that mental age divided by the child's real age, times 100. Turned around, the formula shows what a score of 100 would have meant at each age: exactly the age itself.
| Real age | Mental age at IQ 100 |
|---|---|
| 5 | 5 years |
| 7 | 7 years |
| 9 | 9 years |
| 11 | 11 years |
| 13 | 13 years |
That is one reason it broke down for teenagers and adults, whose test performance stops rising every year. Today's tests compare you with people of the same age instead, so a mental age is only a way to picture a child's score, never a description of an adult.
What an IQ of 100 means for you
It sits in the middle of the average band, which runs from 90 to 109.
- You reason at least as well as the typical person your age on new problems.
- Almost any course or career is open at this level; what you learn and practise matters much more.
- The upper part of this range is close to high average, and practice or a different test could tip it over 110.
How far 100 is from other levels
Why 100 is a milestone: The exact middle of the IQ scale: half of people score higher and half lower.
How 100 compares with nearby scores
Want a score that isn't listed, or the share of people between two scores? Try the IQ calculator.
| IQ | Percentile | Classification | Score this high or higher |
|---|---|---|---|
| 90 | 25th | Average | 75% |
| 95 | 37th | Average | 63% |
| 100 | 50th | Average | 1 in 2 |
| 105 | 63rd | Average | 1 in 3 |
| 110 | 75th | High average | 1 in 4 |
Questions about an IQ of 100
What percentile is an IQ of 100?
An IQ of 100 is at about the 50th percentile, which means it is higher than about 50% of people of the same age.
Is 100 a high IQ?
No. 100 is in the average range. High IQ usually refers to scores of 120 or 130 and above.
Can an IQ of 100 get into Mensa?
Not on its own. Mensa accepts the top 2% on an approved, supervised test, which is usually 130 or above. 100 is 30 points below that.
How common is an IQ of 100 or higher?
About 50% of people score 100 or higher, roughly 1 in 2. In a stadium of 50,000 people, about 25,000 would score at this level or above.
Why is the average IQ set at 100?
Mostly because of history. When David Wechsler introduced age-based scoring in 1939, he kept 100 as the average because earlier IQ tests had already fixed it there. He then placed 90 one probable error below the mean, which gives a spread of about 15 points per standard deviation, the convention modern tests still follow.
What mental age is an IQ of 100?
For a child, 100 means performing exactly like a typical child of the same age, so mental age and real age match. For adults the idea has no meaning, because modern tests compare adults with other adults rather than with an age.
Is 100 above average?
100 is exactly average: the middle of the scale.
What is the difference between an IQ of 100 and 100?
None: 100 is the reference point the whole scale is built around.
Is an IQ of 100 good for a student?
Yes. It is right in the middle of the population, and school results depend at least as much on effort, teaching and interest as on IQ.
See how the middle of the scale is set in our guide to average IQ, or what a good score looks like in what is a good IQ score?. To see how averages differ between countries, read IQ by country. Every score range is in the IQ range chart.
Behind a single score of 100 sit several separate abilities. Read about fluid vs crystallized intelligence, abstract reasoning, spatial reasoning, verbal reasoning and processing speed, or try the free pattern recognition test.
What would you score?
Take the free Assessivo IQ test: 36 questions, 25 minutes, and your estimated IQ score and percentile as soon as you finish.
Take the free IQ test