IQ Percentile Calculator
Enter an IQ score to estimate percentile rank using a normal distribution model.
Note: This is an educational estimate. Actual test norms may vary by test version, age group, and publisher.
What this IQ percentile calculator does
This tool converts an IQ score into a percentile rank. Percentile rank tells you how a score compares with a reference population. For example, a percentile of 84 means the score is higher than about 84% of that population.
By default, the calculator uses the most common IQ scale assumptions: mean = 100 and standard deviation = 15. If you are using a different scoring system, you can adjust those values.
How to use it
- Enter the IQ score you want to evaluate.
- Keep mean at 100 and SD at 15 unless your test uses different norms.
- Click Calculate Percentile.
- Read the percentile estimate and interpretation.
How the percentile is calculated
IQ scores are often modeled as a normal (bell-curve) distribution. The calculator computes:
z = (score - mean) / standard deviation
Then it uses the standard normal cumulative distribution function (CDF) to convert that z-score into a percentile.
Example
If IQ = 115, mean = 100, and SD = 15:
- z = (115 - 100) / 15 = 1.00
- CDF(1.00) ≈ 0.8413
- Percentile ≈ 84.13
So an IQ of 115 is around the 84th percentile under that model.
Quick IQ-to-percentile reference (mean 100, SD 15)
- IQ 70 → about 2nd percentile
- IQ 85 → about 16th percentile
- IQ 90 → about 25th percentile
- IQ 100 → 50th percentile
- IQ 110 → about 75th percentile
- IQ 115 → about 84th percentile
- IQ 120 → about 91st percentile
- IQ 130 → about 98th percentile
- IQ 140 → about 99.6th percentile
Interpreting IQ percentiles responsibly
A percentile is a rank, not a full picture of ability, potential, creativity, motivation, or achievement. Real-world outcomes are influenced by many factors beyond test scores.
Important context
- Different IQ tests may produce somewhat different scores.
- Confidence intervals matter; exact point estimates can fluctuate.
- Age-based norms can affect interpretation.
- Education, health, stress, and language background can influence results.
FAQ
Is percentile the same as percent correct?
No. Percentile rank compares you to other test-takers. Percent correct measures how many items you answered correctly.
Can I use this for any IQ test?
You can use it as an approximation if the test is scaled normally, but always defer to the official norm tables from your specific test.
Does this calculator diagnose anything?
No. This tool is educational and not a diagnostic instrument. Clinical or educational decisions should be made by qualified professionals using standardized procedures.
Bottom line
This IQ percentile calculator gives a fast, mathematically grounded estimate of where a score falls in a distribution. Use it for perspective, but pair it with broader context for meaningful interpretation.