What does the 90th percentile mean?

Being at the 90th percentile means your score is higher than 90% of all scores in the distribution. Only 10% of scores are higher than yours.

Is a higher percentile always better?

It depends on what is being measured. For test scores and income, higher percentiles are typically better. For metrics like response time or error rates, lower percentiles (meaning faster/fewer) are better.

Does this assume a normal distribution?

Yes, this calculator assumes data follows a normal (bell curve) distribution. For non-normal data, percentiles should be calculated directly from the sorted data rather than using z-scores.

Percentile Calculator

Calculate the percentile rank of a score or find the score at a specific percentile using a normal distribution. Useful for standardized tests, grading curves, and data analysis.

A percentile indicates the percentage of scores that fall below a given value.

Score → Percentile

Calculate z = (score - mean) / standard deviation
Look up z in the standard normal distribution
The CDF value × 100 = percentile rank

Percentile → Score

Convert percentile to a decimal (e.g., 90% → 0.90)
Find the z-score using the inverse normal CDF
Score = mean + z × standard deviation

Did this solve your problem?