What does an IQ of 100 mean?
At the average on the reference scale, at approximately percentile 50.
- IQ score
- 100
- Percentile
- 50
- At or above
- 50%
Normal reference · mean 100 · SD 15. These are calculated values, not observed starp population ranks.
Where 100 sits on the IQ scale
There is no distance from the reference mean: (100 − 100) ÷ 15 = 0. The normal cumulative distribution converts that standardized position into percentile 50.
100 is both the mean and the median of this symmetric reference model. Half of the modeled distribution lies below it and half above it. Average here describes a statistical location, not a limit on learning or achievement.
How common is a score of 100?
Approximately 50% of this model lies at or above 100—about 1 in 2. This is a cumulative share, not the chance of scoring exactly 100. A continuous model does not assign a positive probability to one exact value.
IQ 100 is a reference point at the mean. Equal IQ-point gaps do not create equal percentile gaps: the middle of the bell curve contains more area than its ends.
Compare nearby scores
Compare 95 and 100 or calculate 100 on another scale. A small difference between test results is not automatically a meaningful change.
How this relates to starp
starp's current 30-question scoring map produces 100 from 22 correct answers (73.33% correct). That accuracy percentage is different from the normal-model percentile above. The scoring map was calibrated with 12,700 simulated assessments; it is not population norming.
See the scoring method and how raw scores differ from IQ estimates.
Questions about IQ 100
Is 100 a good IQ score?
100 is the center of the reference IQ scale. Whether a result is useful depends on the assessment and what you want to learn from it.
What percentile is an IQ of 100?
On a normal scale with mean 100 and standard deviation 15, 100 corresponds to approximately percentile 50. Around 50% of that model lies at or above it. Use an assessment's own norms for an actual reported rank.
Does an IQ of 100 mean 100% correct?
No. IQ is a scaled score. Percentage correct depends on the questions and scoring rules; percentile describes a relative position. These three quantities are not interchangeable.
Method: NIST's normal-distribution formula. Percentiles here are calculated reference values, not observed starp population ranks. About starp scoring.