Muscle mass percentage is also known as your lean body mass. Your lean body mass is actually composed of your muscle and bone tissue as well as the water in your body and your organs – everything except the fat beneath the surface of your skin. Calculating your muscle mass percentage allows you to determine how much of your total body weight is lean mass versus how much is body fat. The percentage equation also allows you determine your actual lean body weight.
Weigh yourself with a body fat scale. The scale will automatically calculate your percentage of body fat.
Subtract your body fat percentage from 100 to get your lean mass percentage. Here is an example: 100 – 25 percent body fat = 75 percent lean mass.
Divide your lean mass percent by 100 to calculate the decimal for your lean mass percent. Here is an example: 100 / 75 - .75
Multiply your lean mass decimal by your total body weight to calculate your lean mass weight. If you weigh 175 lbs., multiply 175 by .75 for 131.25 lbs. of lean mass.