How to Calculate Square Root 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 “calculate square root 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 cells 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

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. 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. Here is the takeaway for “calculate square root 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

• 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