Percentile Calculator
Find any percentile of a data set, or the percentile rank of a value.
What the Percentile Calculator does
A percentile marks the value below which a given share of the data falls. The 90th percentile is the value that 90% of observations sit below — widely used in performance monitoring, where the tail matters more than the average.
Formula
Position = (n − 1) × p, interpolating between neighboursPercentile rank = (Values below + ½ × Values equal) ÷ n × 100
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Data set | text | Yes | Separate values with commas, spaces or new lines. |
| What do you want to find? | one of 2 options | Yes | — |
| Percentile | % | In some modes | Shown What do you want to find? is Value at a percentile. |
| Value | number | In some modes | Shown What do you want to find? is Percentile rank of a value. |
How to use it
- Choose What do you want to find?.
- Enter Data set.
- Fill in the remaining inputs the form shows for your choice.
- Select Calculate.
Worked example
Response times of 120, 145, 160, 178, 190, 210, 250, 320 ms.
- Data
- 120, 145, 160, 178, 190, 210, 250, 320
- Percentile
- 90
The 90th percentile is 271 ms — 90% of requests completed faster than this.
Frequently asked questions
Why do different tools give different percentiles?
There are several accepted interpolation methods. This one matches Excel's PERCENTILE.INC and NumPy's default, which is the most widely used.
Why report percentiles instead of averages?
Averages hide tails. A 200 ms mean response time can conceal 5% of users waiting three seconds, which the 95th percentile exposes immediately.