IQ 91
What does an IQ of 91 mean?
91 sits just inside the Average band, 1 point above the line with Low Average. Here is what the score means, how rare it is, and why the label matters less than the range around it.
Short answer
An IQ of 91 is a little below average. It is higher than about 27.4% of people, which puts it at the 27.4 percentile. About 1 in 4 people score 91 or lower, and the WAIS-IV labels it Average (90 to 109). It is 0.6 standard deviations below the mean of 100.
Specimen · IQ 91
91IQ
- Classification
- Average
- Percentile
- 27.4
- Rarity
- 1 in 4
- z-score
- −0.60
Curious where you would land? IQ Octopus estimates your IQ from 25 visual puzzles in about 12 minutes.
| Percentile | 27.4 |
| Share scoring 91 or lower | 27.4% (about 1 in 4) |
| Out of 1,000 people | about 274 at or below |
| Standard deviations from the mean (z) | -0.60 |
| WAIS-IV classification | Average (90 to 109) |
| Same percentile, SD 16 scale | 90 |
| Same percentile, SD 24 scale | 86 |
What an IQ of 91 means on the scale
Modern IQ tests report a deviation IQ: scores are standardized so the mean is 100 and the standard deviation is 15 within each age group (Wikipedia: Intelligence quotient). On that scale 91 is 0.6 standard deviations below the mean. It sits inside the 85 to 115 range, where about 68% of people score. (the 68-95-99.7 rule)
In a room of 30 people your age, about 8 would be expected to score 91 or lower. Put another way, about 73 out of every 100 people score above 91.
The Average band: 90 to 109
Average covers 90 to 109 on the WAIS-IV scale (Wikipedia: IQ classification) and is the largest band by far: about 49% of people score in it. Half of everyone tested lands within this 20-point stretch.
The band is centered on 100, the mean of the scale by construction (Wikipedia: Intelligence quotient). 91 is on the lower side of the middle: 9 points below the mean, and 2 above the top of the Low Average band (89). Within this band, differences of a few points are smaller than the error of any test, so 95 and 105 are best read as the same kind of result.
Where 91 sits inside the band
91 is 1 point above the floor of the Average band (90) and 18 points below its ceiling (109). Of the people who score in this band, about 4.3% score below 91, so it is near the bottom of the group that shares its label.
Clinical IQ scores carry measurement error of around plus or minus 5 points at 95% (Wechsler, 2008). A measured 91 is consistent with a true score anywhere from 86 to 96, which is the 17.5 to 39.5 percentile. That range spans two labels, Low Average and Average, so the band name is the least certain part of the result. A short online test has a wider range than a clinical one, so read any single number as the middle of a span.
What an IQ of 91 does and does not predict
An average score means your reasoning on these puzzles matched the typical person your age. It leaves plenty of room for strengths the test does not measure, from knowledge and skills to persistence.
Across large groups, the links are real. General intelligence at age 11 correlated 0.81 with exam results at 16 in about 70,000 English children (Deary, Strand, Smith & Fernandes, 2007), a review of 85 years of workplace research put the link with job performance at 0.51 (Schmidt & Hunter, 1998), and a 2007 meta-analysis found correlations of about 0.56 with education and 0.23 with income (Strenze, 2007). Those describe tendencies across many people. None of them let anyone predict an individual life from one number. The guide to what IQ predicts explains what a correlation of that size means.
Same score, different tests
Older Stanford-Binet forms used a standard deviation of 16, and the Cattell Culture Fair III scale uses 24 (Wikipedia: IQ classification). The same percentile as 91 on a standard-deviation-15 test reads as about 90 on the first and 86 on the second, so check which scale a number is on before comparing scores from different tests.
Nearby scores
| IQ | Percentile | Rarity | Classification |
|---|---|---|---|
| IQ 80 | 9.1 | 1 in 11 | Low Average |
| IQ 85 | 15.9 | 1 in 6 | Low Average |
| IQ 88 | 21.2 | 1 in 5 | Low Average |
| IQ 89 | 23.2 | 1 in 4 | Low Average |
| IQ 90 | 25.2 | 1 in 4 | Average |
| IQ 92 | 29.7 | 1 in 3 | Average |
| IQ 93 | 32 | 1 in 3 | Average |
| IQ 94 | 34.5 | 1 in 3 | Average |
| IQ 95 | 36.9 | 1 in 3 | Average |
| IQ 100 | 50 | 1 in 2 | Average |
| IQ 105 | 63.1 | 1 in 3 | Average |
IQ 90 · IQ 92 · every score on the IQ chart · IQ percentile calculator · the seven classification bands
Sources
- Intelligence quotient. Wikipedia. en.wikipedia.org/wiki/Intelligence_quotient
- IQ classification. Wikipedia. en.wikipedia.org/wiki/IQ_classification
- 68-95-99.7 rule. Wikipedia. en.wikipedia.org/wiki/68%E2%80%9395%E2%80%9399.7_rule
- Wechsler, D. (2008). WAIS-IV Technical and Interpretive Manual. Pearson.
- Deary, I. J., Strand, S., Smith, P., & Fernandes, C. (2007). Intelligence, 35(1), 13-21. doi.org/10.1016/j.intell.2006.02.001
- Schmidt, F. L., & Hunter, J. E. (1998). Psychological Bulletin, 124(2), 262-274. doi.org/10.1037/0033-2909.124.2.262
- Strenze, T. (2007). Intelligence, 35(5), 401-426. doi.org/10.1016/j.intell.2006.09.004