Square Root of 15
The square root of 15 is about 3.873. Square roots reverse squaring and are essential in geometry and the quadratic formula.
No number times itself can equal 15: perfect squares only ever leave 0 or 1 when divided by 4, and 15 leaves 3 — so √15 is irrational, its decimal never ending nor repeating. The ladder fences it between √3 = 9 and √4 = 16, the nearer fence just 1 away against 6 on the far side. Rounded to two places, the estimate is 3.87 — 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 |
|---|---|
| √15 | 3.872983 |
Frequently asked questions
What is the square root of 15?
The square root of 15 is about 3.873. It is the number that, multiplied by itself, gives 15.
Is 15 a perfect square?
No — 15 sits between the perfect squares 9 and 16, so its square root is irrational.
What does √ mean?
√ is the radical sign, short for square root. √15 asks: which number times itself equals 15? Here the answer is about 3.873.