Square Root of 18
The square root of 18 is about 4.2426. Square roots reverse squaring and are essential in geometry and the quadratic formula.
No number times itself can equal 18: perfect squares only ever leave 0 or 1 when divided by 4, and 18 leaves 2 — so √18 is irrational, its decimal never ending nor repeating. The ladder fences it between √4 = 16 and √5 = 25, the nearer fence just 2 away against 7 on the far side. Rounded to two places, the estimate is 4.24 — within one hundredth of the true value. Irrational roots are no curiosity: the diagonal of a unit square is √2, the first irrational anyone ever meets, and every slanted right triangle produces its own.
| Expression | Value |
|---|---|
| √18 | 4.242641 |
Frequently asked questions
What is the square root of 18?
The square root of 18 is about 4.2426. It is the number that, multiplied by itself, gives 18.
Is 18 a perfect square?
No — 18 sits between the perfect squares 16 and 25, so its square root is irrational.
What does √ mean?
√ is the radical sign, short for square root. √18 asks: which number times itself equals 18? Here the answer is about 4.2426.