IQ Test Scale: Score Ranges and What Counts as Genius

How the scale works

An IQ score is a rank turned into a number. The test counts your right answers, compares the count with a large reference group (the norm sample), and places you on a scale where the group's average is 100 and its standard deviation is 15. Pearson, publisher of the Wechsler tests, uses this 100 and 15 scale for the Full Scale IQ and index scores, and its primer explains that a standard score means the same thing on every test normed this way.

The number to look at alongside the score is the percentile: the share of the reference group that scored lower. An IQ of 115 is at about the 84th percentile, which means higher than about 84 out of 100 people in that group. See what an average IQ score is for more on why the middle is always 100.

IQ score ranges and how many people fall in each

The shares below are worked out from the normal curve with an average of 100 and a standard deviation of 15. Each range runs up to the start of the next one (for example, "90 to 109" means 90 up to 110). The labels are the plain ones this site uses on your result. Test publishers use their own, and they differ (see below).

The shares add to 100% before rounding. Within the top band, about 2.1% of people fall between 130 and 144, about 0.13% between 145 and 159, and about 0.003% at 160 or above.

The range a test can report

Every test has a floor and a ceiling. On Pearson's WISC-V (the Wechsler test for children), the Full Scale IQ runs from 40 to 160. The Mensa Norway online test reports scores between 85 and 145. Our test reports scores from 55 to 145. A score printed at a test's ceiling means "at least this high," not an exact value.

Clinical reports also give a range around each score, because no test is exact. In Pearson's WISC-V sample report, a Full Scale IQ of 132 comes with a 95% confidence interval of 125 to 136.

What is genius on an IQ test?

There is no official IQ cutoff for genius. The Pearson score reports we checked label high scores with phrases such as "Very high" and "Extremely High," not "genius."

The idea of a genius line goes back to Lewis Terman, who adapted the Binet-Simon test in the United States. In his 1916 book The Measurement of Intelligence, he suggested a classification table whose top row reads: "Above 140 'Near' genius or genius." In the same book he warned that "the boundary lines between such groups are absolutely arbitrary, a matter of definition only," and wrote: "Intelligence tests have not been in use long enough to enable us to define genius definitely in terms of I Q."

Terman's IQ was also a different number from today's. He defined it as "the ratio of mental age to chronological age," a measure built on how children's abilities grow with age. Modern scores are ranks on the 100 and 15 scale, so his 140 and a modern 140 are not the same thing.

What the normal curve does say is how rare high scores are:

These figures come from the curve, not from counting people. Very few people in any norm sample score this far from 100, so scores at the top of a test are less precise than scores near the middle. Mensa's line for membership, the top 2%, sits at about 131 on this scale: it marks a high score, not genius (see how the Mensa test works). For the most quoted "genius IQ" of all, see whether Einstein ever took an IQ test.

Labels differ between tests

The words attached to a score change from test to test and from one edition to the next:

• Pearson's WISC-V sample report calls a Full Scale IQ of 132 "Extremely High," an index score of 121 "Very High" and one of 111 "High Average." The same materials say scores from 90 to 109 are typically considered average.
• Pearson's WAIS-5 sample report calls a Full Scale IQ of 111 "Above average" and an index score of 124 "Very high."
• Terman's 1916 table called 110 to 120 "Superior intelligence" and 120 to 140 "Very superior intelligence."

So 111 is "High Average" in one Pearson report and "Above average" in another. Compare the number and its percentile, not the label.

Where a score on this test fits

Your result here is placed on the same 100 and 15 scale, but the reference group is the people who take this online test, not a census-matched sample. Until enough people have taken it, the score is a provisional estimate. The How the score works page explains the method, and the WAIS page explains how a clinical IQ test differs.