Percentile Calculator
Find the value at any percentile and the quartiles of a data set.
Results update as you type.
About this calculator
A percentile is the value below which a given percentage of the data falls — the 90th percentile is the point beneath which 90% of the values lie. Percentiles turn a raw number into a rank you can interpret: a test score at the 90th percentile beat 90% of the other scores.
This calculator uses the linear-interpolation method, the same as the spreadsheet PERCENTILE.INC function. It sorts the data, computes a rank of (p ÷ 100) × (n − 1), and if that rank falls between two positions it interpolates linearly between the neighbouring values. It also returns the full five-number summary (minimum, first quartile, median, third quartile and maximum) and the interquartile range.
Worked example: for 5, 7, 8, 12, 14, 18, 21, 25, 30, 35 (ten values) the 90th percentile has rank 0.90 × 9 = 8.1, which lies between the values at positions 8 and 9 (30 and 35); interpolating 0.1 of the way gives 30 + 0.1 × 5 = 30.5. A table below gives the percentile rank of every value, which is handy for growth charts, exam scoring and benchmarking.
Frequently asked questions
How is a percentile calculated?
The data is sorted and a rank of (p/100)·(n − 1) is computed. If that rank is a whole number the value at that position is returned; otherwise the calculator interpolates linearly between the two neighbouring values. This is the inclusive (PERCENTILE.INC) method.
What is the difference between a percentile and a quartile?
Quartiles are just specific percentiles that split the data into four equal parts: the first quartile is the 25th percentile, the second is the 50th (the median) and the third is the 75th percentile.
What is the interquartile range?
The interquartile range (IQR) is the third quartile minus the first — the span of the middle 50% of the data. Because it ignores the top and bottom quarters it is a robust measure of spread and is often used to flag outliers.
What does the 90th percentile mean?
It is the value below which 90% of the data lies, so only 10% of observations are higher. Scoring at the 90th percentile on a test means you did better than about 90% of the other test-takers.
Is the 50th percentile the same as the median?
Yes. The 50th percentile splits the data so that half the values fall below it, which is exactly the definition of the median.
Why might a different tool give a slightly different percentile?
There are several accepted percentile definitions. This calculator uses inclusive linear interpolation (PERCENTILE.INC); the exclusive method (PERCENTILE.EXC) and the nearest-rank method place the percentile slightly differently, so results can vary a little between tools, especially on small data sets.
API — use this calculator from code
Call this calculator as a free JSON endpoint — no key required. Send the field values below as query parameters or JSON. Read the full API docs →
Endpoint
GET https://calculator.free/api/v1/percentile/curl
curl "https://calculator.free/api/v1/percentile/?numbers=5, 7, 8, 12, 14, 18, 21, 25, 30, 35&p=90"JavaScript fetch()
const r = await fetch(
"https://calculator.free/api/v1/percentile/?" + new URLSearchParams({
"numbers": "5, 7, 8, 12, 14, 18, 21, 25, 30, 35",
"p": "90"
}));
const data = await r.json();
console.log(data.results);Results are estimates for general guidance only, not financial, medical or tax advice.