How good is a 91 IQ?
Yes. An IQ of 91 is in the average range, where about half of all people score. It is a little below the exact middle of 100, but well within normal, and a perfectly good result for school, work and everyday life.
Where 91 sits on the bell curve
An IQ of 91 is 9 points below the average of 100, or 0.6 standard deviations. It is higher than about 27% of people of the same age, shown by the shaded area below. Scores in the 90s sit on the steep, crowded slope just left of the peak, so a few points here change your percentile a lot.
On other IQ scales, the same result would be about 90 on a test with a standard deviation of 16, such as older editions of the Stanford-Binet, and 86 on the Cattell scale, which uses 24. Why scales differ.
IQ 91 meaning: a closer look
An IQ of 91 is comfortably inside the average range and higher than about 27% of people. In a group of 100, about 27 would score below it and 73 the same or higher. That might sound modest, but the middle of the bell curve is crowded: the difference between 91 and 100 is only nine points, smaller than the spread you might see if one person took two different tests on two different days. A result of 91 is best read as "average" rather than as a precise position within it.
Iodine, the brain and IQ: what large reviews found
Some of the clearest evidence that nutrition can shape IQ comes from iodine. A 2005 meta-analysis of 37 Chinese studies with 12,291 children found that children in severely iodine-deficient areas without supplementation scored about 12.45 IQ points lower than children in iodine-sufficient areas. A 2013 review of children aged 5 and under estimated gaps of 6.9 to 10.2 points, while warning about weak study designs, missing confounders and small samples, and calling for more randomised trials.
These are averages for whole communities, mostly where deficiency was severe, and most of the evidence is observational. They do not mean that someone with an IQ of 91 was short of iodine, or that iodine would add points to an adult's score. The research points to effects during pregnancy and early childhood, when the brain is developing. For an individual, a 91 IQ is an ordinary average score, shaped by many factors that no single nutrient can explain.
Sources: Qian, M. et al. (2005), "The effects of iodine on intelligence in children: a meta-analysis of studies conducted in China", Asia Pacific Journal of Clinical Nutrition, 14(1), 32 to 42; Bougma, K. et al. (2013), "Iodine and mental development of children 5 years old and under: a systematic review and meta-analysis", Nutrients, 5(4), 1384 to 1416.
What 91 looks like among real people
If you lined up 100 people of your age, about 27 would score lower than 91 and about 73 would score the same or higher. The orange dot marks your place in the line.
Most of the people you meet every day score within a few points of this.
How precise is a score of 91?
No IQ test measures to the exact point. On a professional test, a result of 91 usually comes with a likely range of about five points either way: 86 to 96. That range runs from the 18th to the 39th percentile, and it crosses from low average into average.
In the 90s a few points make a big difference to the percentile, because so many people score here. That is why a gap of a few points between two tests, or two people, usually means very little.
On the Assessivo test, each correct answer is worth about 2.5 points, so 91 falls between two possible results: 90 for 14 correct answers and 93 for 15. How our score is worked out.
So if you scored 91 once, a retest on another day could reasonably land anywhere from 86 to 96. Online tests are less precise still, so treat any online result as a rough estimate.
IQ 91 and mental age in children
Early IQ tests for children worked with a "mental age", the age whose typical performance a child matched. The IQ was that mental age divided by the child's real age, times 100. Turned around, the formula shows what a score of 91 would have meant for children of different ages: working a little behind their years.
| Real age | Mental age at IQ 91 |
|---|---|
| 5 | 4 years 7 months |
| 7 | 6 years 4 months |
| 9 | 8 years 2 months |
| 11 | 10 years |
| 13 | 11 years 10 months |
The same 91 stands for a gap of about 5 months at age 5 but 1 year 2 months at 13, because the formula scales with age. That is one reason it broke down for teenagers and adults, whose test performance stops rising every year. Today's tests compare you with people of the same age instead, so a mental age is only a way to picture a child's score, never a description of an adult.
What an IQ of 91 means for you
It sits near the bottom of the average band, which runs from 90 to 109.
- You reason about as well as most people of your age, with a typical balance of speed and accuracy on new problems.
- Most courses, jobs and everyday decisions sit comfortably within this range of ability.
- Two people at 94 and 104 are closer than the numbers suggest: their likely ranges overlap.
How far 91 is from other levels
How 91 compares with nearby scores
Want a score that isn't listed, or the share of people between two scores? Try the IQ calculator.
| IQ | Percentile | Classification | Score this high or higher |
|---|---|---|---|
| 81 | 10th | Low average | 90% |
| 86 | 18th | Low average | 82% |
| 91 | 27th | Average | 73% |
| 96 | 39th | Average | 61% |
| 101 | 53rd | Average | 1 in 2 |
Questions about an IQ of 91
What percentile is an IQ of 91?
An IQ of 91 is at about the 27th percentile, which means it is higher than about 27% of people of the same age.
Is 91 a high IQ?
No. 91 is in the average range. High IQ usually refers to scores of 120 or 130 and above.
Can an IQ of 91 get into Mensa?
Not on its own. Mensa accepts the top 2% on an approved, supervised test, which is usually 130 or above. 91 is 39 points below that.
How common is an IQ of 91 or higher?
About 73% of people score 91 or higher. In a stadium of 50,000 people, about 36,300 would score at this level or above.
Can iodine supplements raise a 91 IQ?
The research does not show that. The IQ gaps of about 7 to 12 points come from children in communities with iodine deficiency, mostly severe, and the reviews link them to iodine before birth and in early childhood. They do not show that supplements raise an adult's score. If you are worried about your iodine intake, a doctor is the right person to ask.
What mental age is an IQ of 91?
Under the old ratio formula, a 9-year-old with an IQ of 91 would perform like a typical child of about 8 years 2 months, roughly 10 months behind. The idea only works for children: an adult who scores 91 simply did less well than most adults of the same age on the test.
Is an IQ of 91 normal?
Yes. 91 is in the average range of 90 to 109, which covers about half of all people. Nothing about it is unusual.
Why is 91 below 100 if it is average?
100 is the exact middle, but "average" is a band, not a single number. Psychologists call the whole range from 90 to 109 average because the differences within it are small and within a test's margin of error.
Is an IQ of 91 good enough for university?
Yes. Universities select on qualifications, not IQ, and people with average scores succeed on degree courses every year. Effort, interest and study habits make a bigger difference.
Our guide to average IQ explains why the middle is always 100, and what counts as a good IQ score puts the 90s in context. National averages, and why they are disputed, are covered in average IQ by country. Every score range is in the IQ range chart.
Behind a single score of 91 sit several separate abilities. Read about abstract reasoning, spatial reasoning, verbal reasoning, processing speed and fluid vs crystallized intelligence, or try the free pattern recognition test.
What would you score?
Take the free Assessivo IQ test: 36 questions, 25 minutes, and your estimated IQ score and percentile as soon as you finish.
Take the free IQ test