IQ scale and score chart — what your score means

IQ scores are not arbitrary numbers. They are standardized values placed on a well-defined statistical distribution, allowing any individual score to be compared against the performance of the general population. Understanding the IQ scale requires understanding the normal distribution, standard deviations, and percentile ranks.

The standard IQ scale, used by the Wechsler tests and most modern instruments, sets the population mean at 100 and the standard deviation at 15. This means that each 15-point increment above or below 100 represents one standard deviation from the average. For a detailed explanation of what IQ is and how it developed, see our companion article.

When a large, representative sample of people takes an IQ test, the distribution of their scores forms a symmetrical bell-shaped curve. The peak of the curve sits at the mean (100), and scores become progressively rarer as they move further from the center in either direction.

The key property of this distribution is predictability. Exactly 34.13% of scores fall between the mean and one standard deviation above it (100-115), and the same percentage falls between the mean and one standard deviation below (85-100). Combined, 68.26% of all scores fall within one standard deviation of the mean.

At two standard deviations (70-130), the coverage rises to 95.44%. At three standard deviations (55-145), it reaches 99.73%. Scores beyond three standard deviations in either direction are exceptionally rare, occurring in fewer than 3 people per 1,000.

For the mathematical details of how raw test scores are converted into this distribution, see how IQ is calculated.

average (90-109)

Roughly half of the population falls within this range. Individuals here typically handle the cognitive demands of most occupations and educational paths without significant difficulty. An IQ of 100 places a person at the 50th percentile, meaning they score higher than half the population.

high average to superior (110-129)

Scores in this range indicate above-average cognitive ability. Individuals scoring 120 and above (the 91st percentile) often excel in academic settings and are overrepresented in competitive professions. This range encompasses roughly 25% of the population.

gifted (130+)

A score of 130 or above places a person in the top 2.3% of the population. This is the threshold used by many gifted education programs and by Mensa International for membership eligibility (typically the 98th percentile on an approved test). Scores of 145 and above are achieved by approximately 1 in 741 people.

below average and borderline (70-89)

Scores between 80 and 89 are classified as low average. Individuals may benefit from additional support in certain academic or occupational contexts. Scores between 70 and 79 are classified as borderline and may warrant further clinical assessment, particularly if accompanied by difficulties in adaptive functioning.

below 70

Scores below 70 are classified as extremely low. When combined with significant limitations in adaptive behavior, this range may meet the diagnostic criteria for intellectual disability as defined by the DSM-5. A clinical assessment by a licensed psychologist is essential for any diagnostic determination.

IQ classifications are statistical categories, not judgments of human value. A score reflects performance on a specific set of cognitive tasks under specific conditions. Multiple factors influence test performance, including fatigue, anxiety, familiarity with the test format, and the testing environment.

Different IQ tests may also yield slightly different scores for the same individual, because each test emphasizes different cognitive abilities and uses a different norming sample. A score of 115 on the WAIS does not necessarily correspond to 115 on the Stanford-Binet or on a matrix reasoning test. The calculation methodology explains why these discrepancies occur.