IQ Percentiles Explained — Where Do You Rank?

What Are Percentiles?

A percentile indicates what percentage of a comparison group scored at or below a given value. If your IQ score places you at the 75th percentile, that means you scored as high as or higher than 75% of the people in the norming group, and only 25% scored higher than you.

Percentiles are not the same as percentages correct on a test. You could answer 60% of questions correctly and still be at the 90th percentile if the test was very difficult and most people answered fewer than 60% correctly. Percentiles are always about rank order compared to other test-takers, not about raw performance.

For IQ tests, the norming group is typically a large, representative sample of the general population. The major IQ tests (Wechsler, Stanford-Binet) are normed on thousands of people, carefully selected to match the demographics of the country where the test will be used.

IQ Score to Percentile Conversion Table

The following table shows the approximate percentile rank for a range of IQ scores, assuming a mean of 100 and a standard deviation of 15 (the Wechsler scale standard). These values are derived from the cumulative normal distribution:

Note that the rarity column above the mean shows the fraction of people scoring at that level or higher, while below the mean it shows the fraction scoring at that level or lower. The symmetry of the bell curve means that a score of 130 is exactly as rare above the mean as a score of 70 is below it.

How to Interpret Your Percentile

Once you know your IQ percentile, you can understand your score in several practical ways:

• 50th percentile (IQ 100): You are right at the middle. Half of people scored higher, half scored lower. This is the definition of average, and it represents completely normal cognitive functioning. See our detailed guide on what a 100 IQ means.
• 84th percentile (IQ 115): You outperformed roughly 5 out of every 6 people. This is the high end of the average range and represents noticeably above-average reasoning ability.
• 98th percentile (IQ 130): You outperformed roughly 49 out of every 50 people. This is the threshold for giftedness and Mensa eligibility. Read our guide on what a 130 IQ means for more details.
• 16th percentile (IQ 85): About 1 in 6 people score at this level or below. It is in the low average range and still represents normal variation within the population.
• 2nd percentile (IQ 70): This is the clinical threshold that may indicate intellectual disability when combined with deficits in adaptive functioning. See our guide on what a 70 IQ means.

Remember that percentile rankings are relative. Your percentile does not measure your absolute cognitive ability; it measures how you compare to a specific norming group at a specific point in time.

Standard Deviations Explained Simply

The term standard deviation comes up constantly in IQ discussions, and it is simpler than it sounds. A standard deviation is a measure of how spread out scores are from the average. On most IQ tests, the standard deviation is 15 points. This means:

• One standard deviation above the mean (IQ 115): About 84% of people score at or below this level.
• One standard deviation below the mean (IQ 85): About 16% of people score at or below this level.
• Two standard deviations above (IQ 130): About 98% of people score at or below this level.
• Two standard deviations below (IQ 70): About 2% of people score at or below this level.
• Three standard deviations above (IQ 145): About 99.87% of people score at or below this level.

The "68-95-99.7 rule" (also called the empirical rule) provides a quick way to remember the key thresholds:

• 68% of scores fall within one standard deviation of the mean (IQ 85 to 115).
• 95% of scores fall within two standard deviations (IQ 70 to 130).
• 99.7% of scores fall within three standard deviations (IQ 55 to 145).

It is worth noting that not all IQ tests use a standard deviation of 15. The Stanford-Binet, for example, uses a standard deviation of 16, which means a score of 132 on the Stanford-Binet is equivalent to a score of 130 on the Wechsler. Always check which scale your test uses before interpreting your percentile. Our guide on types of IQ tests covers the differences between major test scales.

Important Caveats About Percentiles

While percentiles are a useful way to understand IQ scores, keep these points in mind:

• Percentiles are more precise near the middle than at the extremes. The difference between the 50th and 55th percentile is only about 2 IQ points, but the difference between the 99th and 99.9th percentile is about 15 IQ points. At the extremes, small score changes correspond to large percentile shifts.
• All IQ scores have a margin of error. Professional IQ tests typically report a confidence interval (for example, "your true score is likely between 112 and 122 with 95% confidence"). This means your percentile ranking also has a range, not a single fixed point.
• Online test scores should be interpreted loosely. If you took an online IQ test (including ours), your percentile is an estimate, not a clinical measurement. Use it as a rough guide, not as a definitive ranking. For more on this, see our article on IQ test accuracy and limits.

If you are curious about where you rank, you can take our free IQ test for an estimated score and use the table above to find your approximate percentile. For a more precise result, consider a professionally administered test.