Streamflow Percentile Calculator
Streamflow percentile calculator works out Percentile rank of the value and Values below it from Data set, Value to rank and Tie handling. The default figures on this page give percentile rank of the value of 50.00 %; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
4 steps
- Sorted set (5 values): 10, 20, 30, 40, 50.
- 2 below the score, 1 equal to it, 2 above.
- PR = 100 x (2 + 0.5 x 1) / 5 = 50%.
- Going the other way, the 50th percentile of this set is 30.
Its 5 worked examples are re-run on every release, last on 15 September 2026. What changed
Sources and references
4 sources
What the streamflow percentile calculator calculates
Finds the percentile rank of a value within a data set under the standard mid-rank, strictly-below or cumulative conventions, and works the other direction to give the value at a chosen percentile.
How to use this streamflow percentile calculator
Enter Data set, Value to rank, Tie handling and Percentile to look up (the other direction). Percentile rank of the value updates as you type. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Percentile rank of the value, Values below it and Values equal to it.
The method follows NIST/SEMATECH e-Handbook of Statistical Methods, 7.2.6.2 Percentiles, Hyndman, R.J. & Fan, Y. (1996), "Sample Quantiles in Statistical Packages", The American Statistician 50(4), 361-365, Crocker, L. & Algina, J., Introduction to Classical and Modern Test Theory and USGS, WaterWatch percentile classes for streamflow.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
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Frequently asked questions
What information do I need for the streamflow percentile calculator?
You need Data set, Value to rank, Tie handling, Percentile to look up (the other direction) and Percentile-value method. The page opens with default figures that give percentile rank of the value of 50.00 %, so you can see the scale before entering your own.
What does this streamflow percentile calculator show?
It shows Percentile rank of the value, Values below it, Values equal to it, Values above it, Values in the set, Value at the requested percentile, Minimum and Maximum, with the working and any warnings for your entries.
Can I check how the streamflow percentile calculator result was calculated?
Yes. The “How this is worked out” section shows the calculation steps, and the sources section identifies the references used for the method.