What is a square root?

The square root of a number is the value you multiply by itself to get that number. It is the inverse of squaring. The square root of 9 is 3 because 3 × 3 = 9. It is written with the radical sign √, so √9 = 3.

Examples

• √9 = 3 because 3 × 3 = 9.
• √16 = 4.
• √25 = 5.

Quick facts

• Square roots undo square numbers: since 6² = 36, √36 = 6.
• Perfect squares like 1, 4, 9 and 16 have whole-number square roots.