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What is the Square Root of 81?

The square root of 81 is 9. Calculate another value or review the exact form, nearby perfect powers, and verification.

Answer

Square Root√81 = 9
ExactPerfect squareRational
Exact form9
Perfect squareYes
Number typeRational
Verification92 ≈ 81

On this page

How the answer is calculated

We solve x2 = 81. The resulting value is x = 9.

Verification: 92 ≈ 81.

Simplified radical form

The square root of 81 in simplified radical form is 9.

There are no square factors that can be taken outside the radical, so 9 is already in simplest radical form.

Nearest Perfect squares

PositionBaseValue
Lower or equal981
Upper or equal981

Nearby square roots

NumberSquare root
√788.8317608663
√798.8881944173
√808.94427191
√819
√829.0553851381
√839.1104335791
√849.1651513899

Number properties

Is 81 a perfect square?

Yes. Its square root is the whole number 9.

Is the square root rational or irrational?

9 is rational because it is a whole number.

Visual guide

Square Root function graph

See how the result changes as the input moves across positive and negative values. Square roots are shown for non-negative inputs; cube roots continue through negative inputs.

Common questions

Frequently asked questions

It asks for the number that, when raised to the power of 2, equals 81.