Square Root Calculator
Calculate the square root and cube root of a number.
Square Root
Cube Root
Free to useNo software to install — works in any modern browser.
No signup neededOpen the tool and start straight away.
Runs in your browserNothing you enter is sent to a server.
Works on mobileSame tool on your phone, tablet or desktop.
How it works
- Enter — type or paste your values or text.
- Get the result — it is worked out in your browser.
- Adjust — change the inputs to compare, or copy the result.
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About Square Root Calculator
The square root of a number is the value that, multiplied by itself, gives that number. The square root of 49 is 7, because 7 × 7 = 49.
Perfect squares and the rest
Numbers like 1, 4, 9, 16, 25 and 100 are perfect squares, with whole-number roots. Most numbers aren't: the square root of 2 is about 1.4142, and its decimals go on forever without repeating, so any answer is rounded.
Simplifying roots
In maths classes roots are often written in simplest form. Because 50 = 25 × 2, the square root of 50 is 5√2, which is about 7.071. Look for the largest perfect square that divides the number.
Negative numbers
No real number multiplied by itself gives a negative result, so the square root of a negative number isn't a real number. In higher maths it is written using the imaginary unit i, where i² = −1.
Practical uses
If you know the area of a square, the square root gives the length of each side: a square plot of 100 square metres has sides of 10 metres. Pythagoras' theorem uses square roots to find the long side of a right-angled triangle — with sides of 3 and 4, the third side is √(9 + 16) = √25 = 5 — which builders use to check that corners are truly square. Screen sizes, distances on a map and statistics such as standard deviation all rely on square roots too.
For cube roots and other powers, use the Exponent Calculator: the cube root of a number is the same as raising it to the power 1/3.
Perfect squares and the rest
Numbers like 1, 4, 9, 16, 25 and 100 are perfect squares, with whole-number roots. Most numbers aren't: the square root of 2 is about 1.4142, and its decimals go on forever without repeating, so any answer is rounded.
Simplifying roots
In maths classes roots are often written in simplest form. Because 50 = 25 × 2, the square root of 50 is 5√2, which is about 7.071. Look for the largest perfect square that divides the number.
Negative numbers
No real number multiplied by itself gives a negative result, so the square root of a negative number isn't a real number. In higher maths it is written using the imaginary unit i, where i² = −1.
Practical uses
If you know the area of a square, the square root gives the length of each side: a square plot of 100 square metres has sides of 10 metres. Pythagoras' theorem uses square roots to find the long side of a right-angled triangle — with sides of 3 and 4, the third side is √(9 + 16) = √25 = 5 — which builders use to check that corners are truly square. Screen sizes, distances on a map and statistics such as standard deviation all rely on square roots too.
For cube roots and other powers, use the Exponent Calculator: the cube root of a number is the same as raising it to the power 1/3.
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