What is a square root?

The square root of a number is the value that, multiplied by itself, gives that number. The square root of 25 is 5, because 5 times 5 is 25. Most numbers do not have a whole square root, so the result is a decimal.

Can you take the square root of a negative number?

Not within the real numbers, because no real number multiplied by itself gives a negative result. The square root of a negative number is an imaginary number, which is beyond this calculator. Enter a number of zero or more.

What is a perfect square?

A perfect square is a whole number whose square root is also a whole number, such as 4, 9, 16, and 25. Their roots are 2, 3, 4, and 5. Numbers in between have square roots that are decimals.

Square Root Calculator

This calculator finds the square root of any number you enter, along with its square and cube root, giving you three related results in one place instead of working them out separately. The square root is the value that, multiplied by itself, gives back your original number; the square is your number multiplied by itself; and the cube root is the value that, multiplied by itself three times, gives your number. You simply type a number into the single input field and the calculator updates instantly, showing the square root as the main result, with the square and cube root displayed underneath. This suits schoolwork, checking your own working, or any calculation in geometry, construction or finance where you need to reverse a squared figure or confirm a measurement. Most numbers do not have a whole square root, so expect a decimal answer unless your number is a perfect square like 4, 9, 16 or 25. Enter zero or a positive number; a negative number has no real square root, since no real number multiplied by itself gives a negative result, so the calculator will flag this rather than return a value. The cube root, by contrast, works for negative numbers too, since a negative number cubed stays negative. Use the result alongside the worked example below to check your own calculations by hand.

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Number

square root

Square (n²)0

Cube root0

How it works

The square root reverses squaring. If you square the answer, you get back your number. The calculator also shows the square, which is the number times itself, and the cube root, the value that cubed gives your number.

Worked example

The square root of 50 is about 7.071, because 7.071 times 7.071 is roughly 50. The square of 50 is 2,500, and the cube root of 50 is about 3.684.

Related calculators

Exponent Calculator: powers of a number.
Scientific Calculator: advanced functions.
Pythagorean Theorem Calculator: uses square roots.
Standard Calculator: everyday arithmetic.

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