This article describes the formula syntax and usage of the SQRT function in Microsoft Excel.
Description
Returns a positive square root.
Syntax
SQRT(number)
The SQRT function syntax has the following arguments:

Number Required. The number for which you want the square root.
Remark
If number is negative, SQRT returns the #NUM! error value.
Example
Copy the example data in the following table, and paste it in cell A1 of a new Excel worksheet. For formulas to show results, select them, press F2, and then press Enter. If you need to, you can adjust the column widths to see all the data.
Data 

16 

Formula 
Description 
Result 
=SQRT(16) 
Square root of 16. 
4 
=SQRT(A2) 
Square root of 16. Because the number is negative, the #NUM! error message is returned. 
#NUM! 
=SQRT(ABS(A2)) 
Avoiding the #NUM! error message by first using the ABS function to find the absolute value of 16 and then finding the square root. 
4 