Excel Square Root Function

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. 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. Treat “excel square root function” 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. One habit worth forming early: name the cells that hold your inputs, so the formula reads in plain language instead of a string of cell addresses. A reviewer — or you in three months — can then follow the logic without decoding what B7 and D2 were supposed to mean, which is most of what makes a sheet maintainable.

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. The short version of “excel square root function”: 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 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