Percentile Calculator

A percentile marks the position of a value inside a distribution. The kth percentile is the point below which about k% of the data falls. It answers a different question depending on which way you read it — and the calculator above handles both directions.

Whichever direction you need, the work starts the same way — sort the data — then splits into the rank or the value path.

1. 1

   Sort the data in ascending order

   Percentiles are all about position, so every method begins with the values lined up smallest to largest.

   [64, 71, 73, 78, 82, 85, 88, 90, 95, 99]
2. 2

   Count or locate

   For a rank, count the values below your target. For a value, compute the rank position from p.

   below = 5, equal = 1 · r = ⌈ 90/100 × 10 ⌉ = 9
3. 3

   Apply the formula

   Rank: (below + 0.5·equal) ÷ n × 100. Value: read (or interpolate) the value at the computed rank.

   (5 + 0.5) ÷ 10 × 100 = 55th · sorted[9] = 95
4. 4

   State the method

   For the value at a percentile, note whether you used linear interpolation, nearest rank, or the exclusive method — they can disagree.

   “90th percentile = 95 (nearest rank)”

The biggest source of confusion is that calculators disagree. Here is the 50th percentile of the same six-value set, worked three accepted ways — watch the answer move.

Percentiles turn a raw number into a position, which is exactly what you need to compare across different scales and groups.

Quartiles, quintiles, and deciles are just percentiles at fixed, evenly-spaced points. They divide a sorted distribution into equal groups.

They share a root word and a percent sign, but they answer opposite questions. Mixing them is the most common percentile mistake.

A handful of facts that keep percentile work honest.

Paste a data set and read off the quartiles, deciles, and key percentiles at a glance — the whole distribution in one table.

Common questions