How to Calculate Iqr in 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. The same idea underpins a lot of everyday Excel work, so the few minutes spent getting it right here pay back across every sheet you build afterwards. Treat it as a pattern, not a one-off, and it stops being something you look up and starts being something you reach for. The difference between a quick fix and a sheet you can trust is the extra minute you spend validating “calculate iqr in excel”. Start on a copy or a tiny sample, keep the affected cells visible, and compare the result with the tool above before you touch the real workbook. 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. The point is a calculation you can defend to a CFO or an auditor, but the practical win is that someone else can open the file and understand what happened without asking you.

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. If there is any chance you will reuse this, drop it into a small template tab right now: a labelled input area on the left and the formula beside it, checked once against the tool above. Next time the same question comes up, the answer is a single paste away instead of a rebuild from memory.

In Google Sheets

If you are in Google Sheets rather than Excel, the good news is that the formula shown here is identical and the workflow barely changes — menus sit across the top instead of in a ribbon, and a few function names differ slightly, but anything you build here moves across with little or no rework. Nothing on this page is behind a login or a download: the exact answer is at the top, and the detail below it is there for when you need it. That is the whole promise here — the answer first, and just enough context to make it stick. Here is the takeaway for “calculate iqr in excel”: copy the answer if you are busy, but if you have a spare few minutes, rebuild the example in Excel yourself with the tool above open beside it. That single pass — type it, run it, watch the result move when you change an input — is what turns a formula you found into a technique you trust. Keep your inputs labelled and referenced, never hard-coded, and the same sheet stays correct and auditable as it grows. Done that way, you will not need to look this up again, and you will be the person others ask.

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