| IQ | Percentile | Percentage scoring higher | Position |
|---|---|---|---|
| 100 | 50.0 | 50.0% | Average |
| 120 | 90.9 | 9.1% | High |
| 130 | 97.7 | 2.3% | Very high |
IQ is not a percentage of correct answers or a measure of having a certain percentage of ability. It shows a person's position within a same-age norm group.
IQ has a mean of 100 and a standard deviation of 15
Most modern IQ tests use a standard-score scale on which the mean for a same-age norm group is 100 and the standard deviation is 15. IQ 115 is one standard deviation above the mean, and IQ 130 is two standard deviations above it.
In a normal distribution, about 68.3% of people fall between IQ 85 and 115, and about 95.4% fall between IQ 70 and 130. The farther a score is from the mean, the fewer people receive a score in that range. FSIQ, or Full Scale IQ, is also reported on this mean-100, standard-deviation-15 scale.
Percentiles from IQ 70 to 140
A percentile is the percentage of the same-age norm group at or below a score. At the 91st percentile, about 91% of the group scored at or below that level; viewed from the other side, the score is in approximately the top 9%.
| IQ | Percentile at or below | Percentage scoring higher |
|---|---|---|
| 70 | 2.3 | 97.7% |
| 75 | 4.8 | 95.2% |
| 80 | 9.1 | 90.9% |
| 85 | 15.9 | 84.1% |
| 90 | 25.2 | 74.8% |
| 95 | 36.9 | 63.1% |
| 100 | 50.0 | 50.0% |
| 105 | 63.1 | 36.9% |
| 110 | 74.8 | 25.2% |
| 115 | 84.1 | 15.9% |
| 120 | 90.9 | 9.1% |
| 125 | 95.2 | 4.8% |
| 130 | 97.7 | 2.3% |
| 135 | 99.0 | 1.0% |
| 140 | 99.6 | 0.4% |
These are theoretical values from a normal distribution with a mean of 100 and a standard deviation of 15. For a formal assessment, use the percentile and confidence interval shown in its report. IQ test measurement quality explains differences between test scales and the error contained in a score.
The 10 points between IQ 120 and 130 are not a 10% population difference
IQ 120 is around the 90.9th percentile, or the top 9.1%. IQ 130 is around the 97.7th percentile, or the top 2.3%. Approximately 6.8% of people fall between the two scores.
A 10-point IQ difference is not a 10-percentage-point difference in the population. Nor does IQ 130 mean 30% more ability than IQ 100. IQ points show distance on the score scale, while percentiles show rank within the comparison group.
One reason IQ 130 receives particular attention is that the top 2% is close to the admission threshold commonly used by Mensa. Routes and accepted evidence vary by country, so use the Mensa guide shown for your country.
After locating a score within the population, the value of measuring IQ explains how to use overall IQ and differences between abilities.