Determine your total body mass by stepping onto a scale. Make sure your scale measures in pounds or convert kilograms into pounds.
Multiply 0.15 by your total body mass to calculate total bone mass in pounds. For example, if your total body mass is 140:
140 x 0.15 = 21 lbs. of total bone mass
Obtain your body fat percentage from a trainer or doctor. Take your body fat percentage and divide it by 100 to achieve a decimal number. For example, if your body fat percentage is 10:
10 / 100 = 0.10
Multiply your body fat percentage (in decimal form) by your total body mass. This calculates your current body fat weight.
0.10 x 140 = 14 lbs. of body fat
Add your total bone mass weight and total body fat weight together and subtract the sum from your starting total weight (in pounds). This will calculate your total muscle mass.
21 lbs. of total bone mass + 14 lbs. of body fat = 35 lbs.
140 lbs. of total body mass - 35 lbs. = 115 lbs. of total muscle mass