What does an IQ score mean?
IQ is a standardized comparison with a test’s reference population, usually within an age group. It is not the percentage of questions answered correctly.
Explore a reference IQ score
Uses a normal-distribution model with a mean of 100 and standard deviation of 15. Actual test norms and labels can differ.
50.0 percentile
Approximately 50.0% of modeled scores fall at or below this score, and 50.0% above. This is a reference calculation, not a result from our practice tests.
About 95% between 70 and 130 in this model. The curve displays 55–145; small tails continue beyond the chart.
The shaded area is the approximate percentile. Percentile means relative position—not the percentage of questions answered correctly.
A guide to score ranges
The descriptive bands below are educational groupings on a mean-100, SD-15 scale. Publishers use different classifications. Percentiles are approximate model values at the listed integer boundaries; gaps reflect rounding to whole-number scores.
| IQ score | Approximate percentile | Description |
|---|---|---|
| Below 70 | Below 2.3% | Well below the reference mean |
| 70–84 | 2.3% to below 15.9% | Below the central range |
| 85–115 | 15.9% through 84.1% | Central range (within one standard deviation) |
| 116–129 | 85.7% through 97.3% | Above the central range |
| 130 and above | 97.7% and above | Well above the reference mean |
100 is the reference average
A score of 100 sits near the 50th percentile. A score of 115 is one standard deviation above 100 on this scale, around the 84th percentile. A score of 130 is two standard deviations above it, around the 98th percentile.
Does an IQ of 120 mean 20% more intelligent?
No. IQ is a standardized position on a scale, not a percentage of intelligence. On the model used here, 120 is about 1.33 standard deviations above the mean and near the 91st percentile. That reference position does not measure a person’s overall worth, knowledge, or future success.
Why the test’s scale matters
The same percentile can correspond to different IQ numbers on tests with different standard deviations. Compare the publisher’s norms and percentiles, rather than assuming all scores use a 15-point scale.
One score has uncertainty
A professional report may include a confidence interval and separate domain scores. Testing conditions, language, experience, and the suitability of the assessment affect interpretation. A score alone cannot establish a diagnosis or educational need.
Sources
Mensa International: What is IQ?
OpenStax Psychology 2e: Measures of Intelligence