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