IQ 100: what an average score means

A score of 100 is the mean for the test-taker’s age group. It sits at the 50th percentile, with half of scores above it on the normed scale.

IQ 100 in numbers

Percentileof people score at or below	50.0
Rarityat or above	1 in 2.0
Commonly used band90 to 109	Average

Band labels are the commonly used WISC-V ones, as listed by Smart Kids with Learning Disabilities: Understanding IQ Test Scores. Labels are conventions in common use; each test publisher words its own.

Where it sits on the curve

Shaded: the people who score above it (50.0%).

The same position on other scales

Same percentile on every row; the number changes because the scales use different standard deviations.

Scale	Score	Percentile
SD 15	100	50.0
SD 16	100	50.0
SD 24	100	50.0

Why is the average IQ set at 100?

The average is set at 100 by comparing each test-taker’s score with scores from the same age group. This makes 100 the midpoint of the normed scale, rather than a fixed amount of ability.

A shared midpoint helps readers compare a score with the test’s norm group. The Wechsler scale has a mean of 100 and a standard deviation of 15. See how scores are arranged on the IQ scale.

Why are IQ test norms refreshed?

IQ test norms are refreshed because scores can drift over decades, a pattern called the Flynn effect. Estimates of the rise differ by analysis, so a single rate should not be treated as exact.

Refreshing norms updates the comparison group used to interpret scores. It does not mean every person’s reasoning changed by the same amount.

Does 100 mean the same thing on every IQ scale?

A score of 100 marks the mean on the scales described here, but the spread differs. Older Stanford-Binet editions report scores with a standard deviation of 16; on a scale with a standard deviation of 24, 100 is also the mean.

At 100, the distance from the mean is zero on both scales. Farther from the mean, the same point difference can represent a different share of scores. The IQ standard deviation page explains why the spread matters.

Questions

What percentage of people have an IQ above 100?

Half of scores are above 100, which is the 50th percentile on a normed scale centered at 100. The share above a different score depends on the scale’s spread. Use the IQ percentile calculator to compare a score on a stated scale.

Is an IQ of 100 considered average?

Yes. The nonprofit that lists commonly used WISC-V labels places scores from 90 to 109 in the Average band. A band label applies to that test’s scoring system, so check which test produced a score before applying its labels.

Can IQ 100 mean different things on different tests?

It marks the mean on the scales described here. The standard deviation sets how widely scores spread around that mean, so scores farther from 100 can correspond to different relative positions across scales.