Percentile Calculator

What Is the Percentile Calculator?

A percentile tells you the value below which a given percentage of a data set falls. This tool uses the standard linear-interpolation method (the same one used by Excel's PERCENTILE.INC function).

How to Use This Tool

Enter your data set and the percentile you want (0-100). The value appears instantly.

The Method

Worked Example

A Second Worked Example

The page shows the median of four values. Here is a case where the percentile falls between data points in a less obvious way. Take the hypothetical data 10, 20, 30, 40, 50, which has n = 5, and find the 90th percentile.

The 25th percentile of the same data has index 0.25 × 4 = 1, which lands exactly on the second value, so the answer is 20 with no interpolation needed. When the index is a whole number, the result is always an actual data value. Otherwise it is a blend of the two neighbors, weighted by how close the index is to each.

Interpreting the Result

The output is the value at that percentile, not the rank. If the 90th percentile of a set of delivery times is 46 minutes, then about 90 percent of the deliveries in your data took 46 minutes or less. This is different from "percentile rank," which starts with a value and asks what percentage of the data falls below it. This tool does the first calculation only.

You do not need to sort your data first. The tool orders the values internally, so you can paste them in any order.

Percentile Methods Differ

There is more than one accepted way to define a percentile, and they can give slightly different answers, especially with small data sets. This calculator uses the inclusive linear interpolation method, matching Excel's PERCENTILE.INC. Other tools, such as Excel's PERCENTILE.EXC, some programming libraries, and textbooks that use a nearest-rank rule, may return a different number for the same data. If you need to match a specific source, check which method it uses before comparing numbers.

Practical Uses

• Performance and response times. Teams often report the 90th or 95th percentile to describe how slow the slower cases are, since the average hides them.
• Test scores and growth charts. Percentiles show how a value compares with a group. Interpret official growth or exam percentiles using the published reference tables, not this tool alone.
• Setting thresholds. Choosing a cutoff at the 75th or 90th percentile of your own data is a simple way to define what counts as high.
• Quartiles. Enter 25, 50, and 75 to get the three quartiles, one at a time.

Common Mistakes and Limits

• Entering a fraction. The percentile must be between 0 and 100. Enter 90, not 0.9.
• Small data sets. With only a handful of values, high percentiles are dominated by the maximum and the results are not stable. A 99th percentile from ten values says very little.
• Extremes. The 0th percentile is the minimum and the 100th percentile is the maximum.
• Assuming the answer is in your data. Interpolated results can be values that never appeared in the list, which is normal.
• Duplicate values. Repeated values are kept and counted each time, which is what you want for real data.

Frequently Asked Questions