How to Find a Square Root and Spot a Perfect Square
A square root undoes squaring. This guide explains what square roots mean and how to recognise perfect squares.
What is the Square Root Calculator?
Enter a number and the tool finds the value that, multiplied by itself, gives your number back. It also tells you whether your number is a perfect square, meaning its square root is a whole number, like 144, whose square root is exactly 12.
How to use it
- Enter a number zero or larger.
- Calculate to see its square root.
- Check the note to see if it is a perfect square.
Worked example
The square root of 144 is 12, and 144 is a perfect square.
What is the square root of 144?
It is 12, because 12 times 12 is 144. Since 12 is a whole number, 144 is a perfect square. By contrast, the square root of 2 is about 1.41, which never ends neatly, so 2 is not a perfect square.
Frequently asked questions
Can I find the square root of a negative number?
Not with real numbers. A number multiplied by itself is never negative, so the tool asks for a non-negative number instead.
What is a perfect square?
A number you get by squaring a whole number, such as 1, 4, 9, 16, 25 and 144. Its square root is a whole number with no decimal part.