Percentile Calculator
Find the percentile rank of a value in a data set, or the value that sits at a given percentile.
How it works
Percentile rank = (values below + ½ × values equal) ÷ n × 100 · Value at p = interpolate at rank p ÷ 100 × (n − 1)
A percentile rank says what share of a data set a value beats: the count of smaller values, plus half the ties, divided by the total. Going the other way, the value at a percentile is found by sorting the data and interpolating between the two points that straddle the requested position. The 50th percentile is the median, and the 25th and 75th are the quartiles.
Worked example
In 3, 5, 8, 10, 12, 15, 18, 20 the value 15 has five values below it and one equal, so its percentile rank is (5 + 0.5) ÷ 8 × 100 = 68.75%. Switching modes, the 50th percentile of this list interpolates between 10 and 12 to give 11.
Frequently asked questions
Why do different tools give slightly different percentiles?
There are several accepted definitions — nearest-rank, linear interpolation, and variants that differ at the edges. This calculator uses the common midpoint rule for ranking and linear interpolation for lookup, so answers can differ by a little from a spreadsheet’s method.
Is the 90th percentile the same as the top 10%?
Yes. Being at the 90th percentile means you scored higher than about 90% of the group, which is the same as being in the top 10%. Percentiles describe position within a group, not a raw score.
What is the difference between a percentile and a percentage?
A percentage is a fraction of a total; a percentile is a rank relative to others. Scoring 80% on a test is your share of points, while the 80th percentile means you beat 80% of test-takers — very different ideas.
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For education — check assumptions (sample size, distribution) before using statistics in real decisions.