Iqr Formula Excel

What this does

The interquartile range is the width of the middle half of the data — from the 25th percentile to the 75th. Unlike the full range or the standard deviation, it is unaffected by however extreme the smallest and largest values happen to be, which is why it is the spread measure of choice for skewed data such as salaries, response times and prices. Keep the inputs visible and clearly labelled and the whole thing stays auditable — anyone who opens the file later, including you, can see at a glance exactly what feeds the result and change one assumption without hunting through the formula. Treat “iqr formula excel” as a small repeatable workflow rather than a one-off click you hope to remember next time. Use a small test block before the live file, so any surprise in the affected formula shows up while it is still harmless. 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 turns a calculation you can defend to a CFO or an auditor into a method you can reuse, explain, and defend when the workbook leaves your screen.

A worked example

A column of 100 response times has QUARTILE.INC(range,1) = 12 seconds and QUARTILE.INC(range,3) = 27 seconds, so the IQR is 15 seconds: half of all requests finished within a 15-second band. A single 400-second timeout in the data changes the full range enormously and leaves the IQR untouched. One extreme value destroys the mean and the standard deviation together; the middle-half width is what still describes the data honestly after it arrives. 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. Treat “iqr formula excel” as a small building block rather than a chore. Once the inputs sit in their own cells and the formula reads from them, the same setup answers a dozen related questions with a tweak, and Excel keeps every dependent figure current as the data changes. The tool above is there so you can rehearse and verify before committing anything to a real workbook; the steps and worked example are there so the logic sticks. Get it right once and it stops costing you time — it starts saving it, every time the question comes back around.

Common mistakes

• Mixing QUARTILE.INC for one quartile and QUARTILE.EXC for the other, which produces a width that corresponds to no method at all.
• Comparing an Excel IQR against one computed by hand from the median-of-halves rule and treating the difference as an error; they are different conventions.
• Running it over a range that includes the header or a total row.
• Reporting the IQR as though it were the full range, which understates the spread by definition.

Frequently asked questions