IQ score guide
Percentile
27%
Rarity
1 in 4
this low or lower
Classification
Average
On the standard scale (mean 100, SD 15), a score of 91 sits 0.6 standard deviation below the mean — the 27th percentile, meaning it matches or beats about 27% of the adult population. Test manuals file it under "average" (about half of everyone).
Statistically, scores in this range predict typical performance on abstract, novel material — and next to nothing about any individual life. The middle of the distribution is where the scale has least to say: interests, work habits and circumstances swamp a few IQ points in every direction.
It is a solidly typical score — the range 90–109 holds about half of everyone, and everyday life, most jobs and most goals are built for exactly this range. Within it, small differences carry no practical meaning.
About 1 person in 4 scores 91 or lower; put the other way, roughly 73% of people score above it. It sits 0.6 standard deviation below the mean.
Almost certainly, by a little. Even excellent tests carry ±3–5 points of measurement error, online tests more, and the same person swings several points between good and bad days. Read 91 as "probably between 84 and 98" from a good test — wider from a casual one. Any result quoted without an error range is overclaiming.
Nearby scores: IQ 86 · IQ 90 · IQ 92 · IQ 96 · or see the whole scale.
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