How to Find Interquartile Range in Excel

What this does

QUARTILE splits a dataset into four equal parts, returning the value at whichever boundary you request. Its second argument is an index from 0 to 4, not a percentage, which trips people who come to it from PERCENTILE. Its practical value is the interquartile range: quartile 3 minus quartile 1 gives the spread of the middle half, and the standard outlier rule flags anything beyond 1.5 IQRs outside those bounds. That is also exactly what a box plot draws, so QUARTILE is how you replicate one numerically. Most people learn this as a sequence of clicks and forget it by next week; learning it as a pattern instead is what lets you apply it to the next, slightly different version of the problem without starting from scratch. That is the difference this page is trying to make. For “find interquartile range in excel”, the reliable version is a short checking loop, not just the first command that appears to work. Run it on a deliberately small range first, watch how the affected cells change, and only then apply the same setup to the full sheet. When a formula is involved, keep the inputs labelled beside it, reference cells instead of typing values, and apply number formatting only after the result checks out. That is what makes a data step that keeps your analysis trustworthy useful in real work: repeatable, auditable, and not dependent on memory or luck.

A worked example

Order values in B2:B200: =QUARTILE.INC(B2:B200, 1) and =QUARTILE.INC(B2:B200, 3) give the quartile bounds, and their difference is the IQR. An upper outlier threshold is =QUARTILE.INC(B2:B200,3) + 1.5*(QUARTILE.INC(B2:B200,3)-QUARTILE.INC(B2:B200,1)). QUARTILE is the numeric basis of the box plot and the standard outlier rule, which makes it the fastest way to describe spread without assuming a distribution. A practical tip before you scale it up: build it once on a small block of test data, confirm the number against the tool on this page, and only then point it at your real sheet. That one habit catches almost every mistake while it is still cheap to fix, long before a wrong figure reaches a report or a colleague.

In Google Sheets

Everything above works in Google Sheets too. Excel and Sheets share the formula syntax used here; only the surrounding menus are arranged differently. That portability is deliberate — learn it once and it follows you between the two tools and across Windows and Mac. Keep this page bookmarked for the next time the same question comes up. Better still, repeat the steps once in your own workbook — doing it yourself is what turns a copied answer into something you remember. The short version of “find interquartile range in excel”: the answer is at the top of this page, the tool proves it on your own numbers, and the sections above explain why it holds so the next variation does not stump you. Excel rewards people who reference cells instead of typing values and who keep inputs separate from formulas, because that is what makes a result you can audit months later. Build it once, deliberately, with the live tool as a check, and you convert a one-off lookup into a reusable skill — which is the whole point of learning the why and not just the what.

Common mistakes

• Passing 0.25 instead of 1 — the argument is an index from 0 to 4, not a proportion.
• Using QUARTILE.EXC on small samples where the boundary is undefined, which returns #NUM!.
• Reporting quartiles on a tiny dataset, where they are unstable and a simple sorted list says more.

Frequently asked questions