What is the correct way to raise a number to a power in Java?

General Discussions
1

I’m trying to calculate BMI in my Java program, but the output seems incorrect. When I check the result with a calculator for this formula:

(10 / ((10 / 100) ^ 2))

I get 1000, but in my program, I get 5.

Here’s my code:

bmi = (weight / ((height / 100) ^ 2)); // Incorrect calculation

It looks like the exponentiation (^2) isn’t working as expected.

How should I correctly raise a number to a power in Java to fix this issue?

2

I see where things are going wrong. In Java, the ^ operator does not perform exponentiation—it’s actually a bitwise XOR operator, which explains why your calculation is incorrect.

Don’t worry! There are a few proper ways to raise a number to a power in Java.

Java provides the Math.pow(base, exponent) method, which is the correct way to raise a number to a power.

bmi = (weight / Math.pow((height / 100.0), 2)); // Correct power calculation

:white_check_mark: Why use this?

Math.pow(x, y) correctly computes x^y. It ensures floating-point division (height / 100.0 instead of height / 100, which would cause integer division).

3

Since you’re only raising a number to the power of 2, you can simply multiply it by itself instead of using Math.pow().

double heightInMeters = height / 100.0;
bmi = (weight / (heightInMeters * heightInMeters)); // Squaring manually

:white_check_mark: Why use this?

Faster and more efficient than Math.pow() when squaring. Avoids unnecessary function calls for a simple exponentiation.

4

If you need to raise a number to a power without using Math.pow(), you can implement a simple loop-based exponentiation.

public static double power(double base, int exponent) {
    double result = 1;
    for (int i = 0; i < exponent; i++) {
        result *= base;
    }
    return result;
}

And modify your BMI calculation:

double heightInMeters = height / 100.0;
bmi = (weight / power(heightInMeters, 2)); // Using custom power method

:white_check_mark: Why use this?

Good learning exercise to understand exponentiation logic. Can be modified for integer-based exponentiation.