How do you calculate fat mass?

To calculate fat mass accurately, it is essential to understand the relationship between body fat percentage and total body weight. The correct equation involves multiplying the body fat percentage (expressed as a decimal) by the scale weight. This approach allows for the determination of the actual weight of the fat in the body.

For instance, if the body weight is 150 pounds and the body fat percentage is 20%, the calculation would look like this: first convert 20% to a decimal (0.20), and then multiply it by the total weight (150 pounds). This calculation reveals that the fat mass is 30 pounds, which is the correct method for determining fat mass using the provided metrics.

The other options misrepresent the relationship between body fat percentage and total weight, leading to incorrect calculations or definitions that do not yield a valid measure of fat mass. In particular, simply adding body fat percentage to scale weight or subtracting lean body mass does not provide a meaningful or accurate measurement for fat mass.