SQRT Function in Microsoft Excel: Examples, Pitfalls & Compatibility
SQRT in Microsoft Excel: calculate the nonnegative real square root and identify inputs outside the real-valued domain. Includes worked examples and application-specific cautions.
Verification status: Official documentation referenced; example outcomes independently reasoned or arithmetically checked where stated. Not executed in Microsoft Excel. How formula examples are checked
Quick answer: Use SQRT in Microsoft Excel to calculate the nonnegative real square root and identify inputs outside the real-valued domain. The official SQRT reference is the source for the function definition and platform-specific rules described below.
Syntax and arguments
=SQRT(number)
number (required): The nonnegative numeric value whose square root is required.
Examples use English function names, comma argument separators and decimal points. Adapt formula separators to your workbook settings, not punctuation inside quoted text.
When to use it
Use SQRT to recover a side length from a square area or to calculate a Euclidean distance from squared components. The function returns the principal nonnegative root, not both algebraic roots of an equation.
Three worked examples
Each example is independent. Where input cells are listed, enter those values first; otherwise the formula is self-contained. Expected outputs are independently checked calculations or documented error expectations, not captured results from Microsoft Excel.
Example 1: Recover a side length
=SQRT(225)
Expected result: 15.
A square with area 225 square units has a side length of 15 units.
Example 2: Calculate distance from perpendicular components
=SQRT(6^2+8^2)
Expected result: 10.
The squared components sum to 100; its principal root is 10. Both components must use the same unit.
Example 3: Recognize an invalid real input
=SQRT(-36)
Expected result: #NUM! (the documented error case).
The documented error is the expected result, not a test failure. Using ABS would answer a different question.
Put it to work safely
Keep units consistent before squaring or taking roots. An area measured in square centimetres produces a side length in centimetres. If a calculation unexpectedly produces a negative radicand, investigate the input or model. Wrapping the value in ABS changes the mathematical problem and should not be used merely to hide an error.
Common mistakes and fixes
A negative value produces an error. This real-valued function cannot supply the square root of a negative real input. Both references document NUM for that case.
Only the positive root appears. The function supplies the principal root. An equation that has two roots requires separate mathematical handling.
A perfect square appears approximately correct. Check the original value and any preceding calculation. A displayed rounded input may differ from the stored value.
Microsoft Excel-specific notes
Microsoft documents the NUM error for negative inputs. Although its help illustrates applying ABS, use that transformation only when the magnitude is genuinely the intended input, not as an automatic error repair. See the vendor reference for the current definition.
Excel and Google Sheets comparison
The positive integer and documented negative-input cases form a small common test set. Neither this guide nor the paired article certifies every floating-point extreme or complex-number workflow.
Compare the SQRT guide for Google Sheets and its official documentation. Having a guide in both libraries establishes two documented references, not a certificate of identical behavior across releases, locales or file conversions.
Related guides
Evidence and testing scope
Editorial verification: Official references retrieved on 2026-10-12. The three worked cases are included in this release’s reproducible Python checking suite. It checks the stated arithmetic, calendar or text model and the expected documented error classification; it is not the Microsoft Excel calculation engine. No native application run, UI screenshot, maximum-size benchmark or cross-version certification is claimed. Review the editorial testing standards before relying on a formula in a critical workbook.