To calculate $15^2$, you simply multiply 15 by itself:

$15^2 = 15 \times 15 = 225$

So, $15^2 = 225$.

Would you like more details or have any questions?

Here are 5 related questions:

1. How do you calculate the square of a number?
2. What is the square root of 225?
3. How do you square a negative number, like $(-15)^2$?
4. What is the general formula for squaring a binomial, such as $(a + b)^2$?
5. How do you express $15^2$ in scientific notation?

Tip: Remember that squaring a number means multiplying the number by itself.