Quartile & IQR Calculator (Five-Number Summary)

By in
Updated October 27, 2026
10 numbers — separate with commas, spaces or new lines
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Edit the numbers above — results update as you type.

How to use this calculator

Paste your data. You get the five-number summary (min, Q1, median, Q3, max), the IQR and the outlier fences.

Method

Quartiles are found by linear interpolation between sorted values — the method used by Excel’s QUARTILE.INC.

Worked example

Data: 1, 3, 5, 6, 7, 8, 9, 12, 15, 21

  • Q1 = 5.25, median = 7.5, Q3 = 11.25
  • IQR = 6
  • Fences: -3.75 and 20.25 → 21 is an outlier

Box plots

A box plot draws a box from Q1 to Q3 with a line at the median, and “whiskers” to the smallest and largest values inside the fences. Points beyond the fences are drawn individually as outliers.

Frequently asked questions

What is the interquartile range?

Q3 − Q1, the spread of the middle 50% of the data. It is not affected by extreme values.

How are outliers identified?

A common rule flags values below Q1 − 1.5×IQR or above Q3 + 1.5×IQR.

Why do calculators give different quartiles?

There are several methods. This one uses linear interpolation, the same as Excel's QUARTILE.INC and PERCENTILE.INC.

Embed this calculator

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