You can calculate your body fat percentage from a standard formula that incorporates a few specific body measurements. This formula varies by gender, because the distribution of body fat differs between men and women. Knowing your body fat percentage can help you assess your physical fitness more accurately than working with your total body weight, because a physically fit person tends to have more muscle weight than one who is sedentary.
Step 1
Gather measurements that don’t depend on gender. Weigh yourself in pounds on a bathroom scale, and measure the circumference of your waist in inches at the level of your navel.
Step 2
Take additional measurements if you’re a woman. Measure in inches the circumference of your hips, forearm and wrist at their widest points.
Step 3
Calculate your lean body mass if you’re a man. This calculation uses the formula (1.082 x weight) - (4.15 x waist) + 94.42.
This example assumes you weigh 165 lb. and have a 31-inch waist. Your lean body mass is therefore (1.082 x 165) - (4.15 x 31) + 94.42 = 144 lb.
Step 4
Compute your lean body mass if you’re a woman. This computation uses the formula (0.732 x weight) - (0.157 x waist) - (0.249 x hips) + (0.434 x forearm) + (wrist / 3.14) + 8.987.
This example assumes you weigh 147 lb. and have a 32-inch waist. You have 37-inch hips, a 9-inch forearm and a 6-inch wrist. Your lean body mass is therefore (0.732 x 147) - (0.157 x 32) - (0.249 x 37) + (0.434 x 9) + (6 / 3.14) + 8.987 = 108 lb.
Step 5
Convert your lean body mass to your body fat percentage. This conversion uses the formula (weight - lean body mass) x 100 / (weight).
This example assumes you weigh 165 lb. and have a lean body mass of 144 lb. Your body fat percentage is therefore (165 - 144) x 100 / 165 = 12.7 percent.
Things You'll Need
- Bathroom scale
- Tape measure
- Calculator
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