The square root of 81 is 9.
The square root of 81 is 9.
Because 9 × 9 = 81, 81 is a perfect square and its root is a whole number.
You can check it by squaring the result: 9² ≈ 81.
| √81 | = 9 |
| 9² | = 81 |
| ∛81 | = 4.326749 |
| Number | Square root | Note |
|---|---|---|
| 40 | 6.324555 | |
| 49 | 7 | perfect square |
| 50 | 7.071068 | |
| 64 | 8 | perfect square |
| 72 | 8.485281 | |
| 81 | 9 | this page |
| 100 | 10 | perfect square |
| 121 | 11 | perfect square |
The square root of 81 is 9.
Yes. 9 × 9 = 81.
Rational, because it is the whole number 9.
The cube root of 81 is about 4.326749.
Yes. Use the calculator on this page, or open the full free Scientific Calculator with memory, history and keyboard support.