In Excel: use =SQRT(number) — it returns the positive square root, so =SQRT(144) returns 12. Negative input returns #NUM!.
On this page8
Syntax
Arguments
| Argument | required / optional | Description |
|---|---|---|
number | required | The value to take the square root of. Negative input returns #NUM!. |
Related functions
Click the result cell and type =SQRT(.
Select the value or nest the calculation that produces it.
Close the bracket and press Enter.
If negatives are possible and meaningless, wrap the input in ABS to avoid #NUM!.
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. The difference between a quick fix and a sheet you can trust is the extra minute you spend validating “sqrt function in excel”. Start on a copy or a tiny sample, keep the affected formula visible, and compare the result with the outcome you expected 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
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. Check the referenced cells, argument order and result type in your workbook. Start with the worked example before changing an input, then compare the changed result with the calculation you expected. An error value or a result of a different type is a reason to inspect the inputs and arguments.
In Google Sheets
Google Sheets support for this task has not been verified. Check the function, arguments and workflow in the target product before transferring the example. Matching formula notation does not establish identical behaviour. 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 and the detail above shows why it holds — so the next time a colleague asks, you can answer without reaching for search. For “sqrt function in excel”, keep the input cells and the result visible while you check the formula in Excel. Follow the worked example and change one input at a time. The steps explain the workbook calculation; this page does not run a live calculator for that task.
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
Why does SQRT return #NUM!?
The input is negative. Wrap it in ABS if the sign is irrelevant, or fix the upstream calculation if it should not have gone negative.
How do I get a cube root?
SQRT only does square roots. Use =POWER(A2, 1/3) for a cube root, or 1/n for any other.
Is SQRT the same as raising to 0.5?
Yes, =SQRT(A2) equals =POWER(A2, 0.5) and =A2^0.5. SQRT is simply the clearest of the three.