📊 Percentile Calculator
By ToolNimba Editorial Team · Updated 2026-06-19
The value mode uses linear interpolation; the rank mode uses (below + half of equal) / n.
A percentile tells you where a value sits within a data set: the 90th percentile is the point below which 90% of the values fall. This calculator works two ways. Paste a list of numbers and a percentile (k) to get the value at that percentile, or paste a value to get its percentile rank. It sorts your data, applies the linear interpolation method, and shows the sorted list so you can check the result by eye.
What is the Percentile Calculator?
A percentile is a position measure that splits ordered data into 100 equal parts. The kth percentile is the value at or below which roughly k percent of the data lies. Percentiles are widely used because they describe where a single point falls relative to everything else, without assuming the data follows any particular shape. The 25th, 50th, and 75th percentiles are the three quartiles, and the 50th percentile is the median.
There is more than one accepted way to compute a percentile, which is why two tools can give slightly different answers. This calculator uses the linear interpolation method on the n minus 1 basis (the same convention as the inclusive PERCENTILE.INC function in spreadsheets and the NIST linear method). It first sorts the data, then finds a fractional rank with rank = (k / 100) x (n - 1). If that rank lands between two data points, it interpolates linearly between them, so the percentile does not have to be an actual member of your set.
Percentile rank runs the question in reverse: given a value, what percentage of the data falls below it? A common, symmetric definition counts the values strictly below the target plus half of the values equal to it, divided by the total count, times 100. The half-weighting of ties keeps the rank fair when a value appears more than once. Percentile rank is the figure you see on standardized test scores, growth charts, and benchmark reports, where being in the 95th percentile means you scored at or above about 95% of everyone measured.
When to use it
- Finding the value that marks the top 10% (90th percentile) of test scores, salaries, or response times.
- Reporting a percentile rank, such as telling a student they scored higher than 88% of the cohort.
- Computing quartiles (25th, 50th, 75th) to summarize the spread of a data set without being thrown off by outliers.
- Setting service-level targets, for example a 95th percentile latency budget for a web service.
How to use the Percentile Calculator
- Pick a mode: "Value at percentile" to find a value, or "Percentile rank of a value" to find a rank.
- Paste your numbers, separated by commas, spaces, or new lines.
- In value mode, enter the percentile k from 0 to 100. In rank mode, enter the value to rank.
- Read off the result, the count, the minimum and maximum, and the sorted data.
Formula & method
Worked examples
Find the 25th percentile of the data set 2, 4, 4, 4, 5, 5, 7, 9 (n = 8).
- Sort the data (already sorted): 2, 4, 4, 4, 5, 5, 7, 9
- rank = (25 ÷ 100) x (8 - 1) = 0.25 x 7 = 1.75
- The rank 1.75 lies between index 1 (value 4) and index 2 (value 4), with fraction 0.75
- value = 4 + 0.75 x (4 - 4) = 4
Result: The 25th percentile is 4.
Find the 90th percentile of the same data set 2, 4, 4, 4, 5, 5, 7, 9.
- rank = (90 ÷ 100) x (8 - 1) = 0.9 x 7 = 6.3
- The rank 6.3 lies between index 6 (value 7) and index 7 (value 9), with fraction 0.3
- value = 7 + 0.3 x (9 - 7) = 7 + 0.6 = 7.6
Result: The 90th percentile is 7.6.
Find the percentile rank of the value 5 in 2, 4, 4, 4, 5, 5, 7, 9.
- Count values below 5: there are 4 of them (2, 4, 4, 4)
- Count values equal to 5: there are 2 of them
- PR = (4 + 0.5 x 2) ÷ 8 x 100 = 5 ÷ 8 x 100
- PR = 0.625 x 100 = 62.5
Result: The value 5 sits at the 62.5th percentile.
Common percentiles and what they mean
| Percentile | Also called | Meaning |
|---|---|---|
| 25th | First quartile (Q1) | 25% of values fall at or below this point |
| 50th | Median (Q2) | The middle value; half the data is below it |
| 75th | Third quartile (Q3) | 75% of values fall at or below this point |
| 90th | Top decile boundary | Only 10% of values are higher |
| 95th | 95th percentile | Often used for latency or score thresholds |
Percentiles of the example set 2, 4, 4, 4, 5, 5, 7, 9 (linear interpolation)
| Percentile (k) | Value |
|---|---|
| 0 | 2 |
| 25 | 4 |
| 50 | 4.5 |
| 75 | 5.5 |
| 90 | 7.6 |
| 100 | 9 |
Common mistakes to avoid
- Forgetting to sort the data first. A percentile is a position in ordered data, so the list must be sorted before you read off or interpolate a value. This tool sorts automatically and shows the sorted list, but doing it by hand on unsorted data gives a wrong answer.
- Confusing the percentile with the percentile rank. The kth percentile is a value (the 90th percentile might be 7.6). A percentile rank is a percentage that describes where one value sits (a score of 5 might be the 62.5th percentile). They answer opposite questions, so make sure you are in the right mode.
- Expecting every tool to agree exactly. There are several accepted percentile methods (inclusive, exclusive, nearest-rank). They can differ by small amounts, especially on small samples. This calculator uses the linear interpolation, n minus 1 method, the same as the inclusive spreadsheet function.
- Reading the 100th percentile as "better than everyone". Under this method the 0th percentile is the minimum and the 100th percentile is the maximum, so the very top value is at the 100th percentile. Percentile rank, by contrast, rarely reaches a flat 100% because of the half-weighting of ties.
Glossary
- Percentile
- A value below which a given percentage of the data falls. The kth percentile marks the k% point of the ordered data.
- Percentile rank
- The percentage of data values that fall at or below a given value, a way to describe where a single point sits.
- Quartile
- The 25th, 50th, and 75th percentiles, which divide ordered data into four equal parts.
- Median
- The 50th percentile, the middle value of the data when it is sorted.
- Linear interpolation
- Estimating a value that falls between two known data points by moving along the straight line between them.
Frequently asked questions
What is a percentile?
A percentile is a value below which a certain percentage of a data set falls. The 90th percentile, for example, is the value at or below which about 90% of the data lies. Percentiles describe relative position without assuming the data has any particular distribution.
How do I calculate the value at a given percentile?
Sort the data, then compute rank = (k / 100) x (n - 1), where n is the number of values. If the rank is a whole number, take that sorted value. If it falls between two values, interpolate linearly between them. This tool does all of that automatically.
What is the difference between a percentile and a percentile rank?
A percentile is a value: the kth percentile is the point at the k% position. A percentile rank is a percentage: it tells you what fraction of the data falls at or below a specific value. One starts from a percentage and returns a value, the other starts from a value and returns a percentage.
Which percentile method does this calculator use?
It uses linear interpolation on the n minus 1 basis, the same inclusive method as the PERCENTILE.INC spreadsheet function and the NIST linear definition. Under it the 0th percentile is the minimum and the 100th percentile is the maximum.
Why do different calculators give slightly different percentiles?
Because there are several legitimate definitions (inclusive, exclusive, and nearest-rank among them). They agree on large data sets but can differ on small samples. Always note which method a result used before comparing figures from two sources.
How is percentile rank calculated when a value repeats?
This tool counts the values strictly below the target, adds half of the values equal to it, divides by the total count, and multiplies by 100. The half-weighting of ties keeps the rank symmetric and fair when a value appears more than once.