Square Root Formula in Excel

What this does

SQRT returns the positive square root of a number. It errors with #NUM! on negative input rather than returning a complex result, which is why the common defensive form is =SQRT(ABS(A2)) when the sign is known to be noise. In statistics it is the step that turns a variance into a standard deviation, and it appears in distance and standard-error formulas for the same reason. It is equivalent to =POWER(A2, 0.5), but SQRT states the intent plainly. 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. Treat “square root formula in 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

Converting a variance of 18.49 into a standard deviation: =SQRT(18.49) returns 4.3. Standard error from a standard deviation of 12 across 36 observations: =12/SQRT(36) returns 2. Straight-line distance between two points: =SQRT((x2-x1)^2 + (y2-y1)^2). SQRT is the step that converts squared quantities back into the original units, which is why every standard deviation and distance formula ends with it. 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

Google Sheets handles this almost identically to Excel. The formula syntax above is the same, and the menu lives under a slightly different label rather than a ribbon tab. Use the platform toggle at the top of the page to switch every keyboard shortcut between Windows and Mac, and expect at most cosmetic differences in naming. The aim was to get you unstuck fast and leave you a little more capable than a copy-paste would. The answer is at the top, the tool proves it, and the detail above shows why it holds — so the next time a colleague asks, you can answer without reaching for search. Treat “square root formula in 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

• Passing a negative number, which returns #NUM! — Excel has no real square root for it.
• Taking the square root of a sum where each term needed squaring first; the squares go inside the brackets.
• Using SQRT where a different root was meant — a cube root needs =POWER(A2, 1/3).

Frequently asked questions