We use Excel SQRT function when we want to get the square root of a positive number. The SQRT function will return an error if supplied with a negative number. To fully understand how this function works, read this step-by-step guide on how to use the Excel SQRT function.

Figure 1: Use of SQRT function

Syntax of the formula


Where number refers to the number of which you want to get the square root of.

The function only works with positive numbers, and will return a positive result. It will return a #NUM! error if applied on a negative number, as shown in the example above.

But you can still get the square root of a negative number by wrapping the number in the ABS function.

Example: Finding square root of negative number

Figure 2: Square root of negative numbers

Notice that the numbers in column A are all negative numbers. We have wrapped the numbers in an ABS function to get the square root of the negative numbers. The formula in cell B2 in the example above looks like below:


We then copy down the formula to apply it to all the other cells.