Quartiles & Percentiles
Local ProcessingCalculate the first quartile (Q1), median (Q2), and third quartile (Q3) of a dataset.
How It Works & Processing Standards
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Finds the values at the 25%, 50% and 75% points of sorted data, or at any p% point you choose.
The method is R-7 (linear interpolation). Software that uses another method may give slightly different values.
What You Can Do
- Quartiles
- Q1 (25%), Q2 (median, 50%) and Q3 (75%) at once.
- Percentile
- Enter p from 0 to 100 to get the pth percentile, such as the top-10% cutoff.
How to Use Quartiles & Percentiles
- 1Choose a calculationPick quartiles or percentile.
- 2Enter numbersAny order is fine; values are sorted for you. For a percentile, also enter p.
- 3Read the resultPoints between two values are found by linear interpolation.
Examples
Quartiles of nine values
Input: 3, 7, 8, 5, 12, 14, 21, 13, 18
Result: Q1 7, Q2 12, Q3 14
90th percentile
Input: 55, 60, 70, 80, 90 / p = 90
Result: 86
Common Use Cases
- Top and bottom 25% cutoffs of a score distribution
- Outlier fences with the IQR (Q1 − 1.5·IQR, Q3 + 1.5·IQR)
- 90th or 95th percentile response times
Frequently Asked Questions (FAQ)
Why does another calculator give a different Q1?
There are several quartile methods. This tool uses R-7, the same as Excel QUARTILE.INC.
What do I enter for p?
A number from 0 to 100. p = 50 is the median.