Online Square Root Calculator

The square root of a number is whatever value, multiplied by itself, gives you that number. So the square root of 9 is 3, because 3 × 3 = 9. The square root of 2 is roughly 1.4142, because 1.4142 × 1.4142 ≈ 2. Most square roots of non-perfect-square numbers are irrational — they go on forever without repeating. This calculator shows them to several decimal places, which is accurate enough for nearly any practical purpose.

The most common real-world use is geometry. If you know the area of a square, the square root gives you the side length. If you have a right triangle and know two sides, the Pythagorean theorem (a² + b² = c²) requires square roots to find the third. Architecture, woodworking, and basic engineering all use this constantly.

It also shows up in statistics (standard deviation calculations involve square roots), physics, and finance (certain compound interest formulas). Students encounter it constantly in algebra and geometry homework.

√1 = 1, √4 = 2, √9 = 3, √16 = 4, √25 = 5, √36 = 6, √49 = 7, √64 = 8, √81 = 9, √100 = 10, √121 = 11, √144 = 12. These come up so often in math and everyday calculations that recognizing them on sight saves a lot of time. Everything else you can look up here.

You can't take the square root of a negative number in standard arithmetic — there's no real number that multiplied by itself gives a negative result. (Mathematicians handle this with imaginary numbers, but that's beyond the scope of a general-purpose calculator.) If you enter a negative number here, you'll get an error rather than a nonsense answer.