Your body fat percentage is generally a better method of assessing your fitness than your total body weight. Your total body weight may change little and can even increase when you began a fitness program because you can lose fat and gain muscle at the same time. You can calculate your body fat percentage with a few basic measurements using formulas available at DaveDraper.com, a fitness website. These calculations are accurate to about 3 percent.
Step 1
Measure your forearm, wrist and hips circumferences at their widest points if you're a woman. Everyone must also measure the circumference of the waist at navel level. All of these measurements must be in inches.
Step 2
Weigh yourself when you first wake up so that your water weight is at its lowest level of the day. Use a scale that measures weight in pounds.
Step 3
Compute your lean body weight with this equation if you're a woman: (weight x 0.732) - (waist measurement x 0.157) + (forearm measurement x 0.434) + (wrist measurement / 3.14) - (hip measurement x 0.249) + 8.987.
Assume you have the following measurements: 123-lb. weight, 31-inch waist, 9-inch forearm, 6-inch wrist and 39-inch hips. Your lean body weight is therefore (123 x 0.732) - (31 x 0.157) + (9 x 0.434) + (6 / 3.14) - (39 x 0.249) + 8.987 = 90 lbs.
Step 4
Calculate your lean body weight with this equation if you're a man: (weight x 1.082) - (waist measurement x 4.15) + 94.42.
Assume you have the following measurements: 171-lb. weight and 33-inch waist. Your lean body weight is therefore (171 x 1.082) - (33 x 4.15) + 94.42 = 142 lbs.
Step 5
Derive your body fat percentage from your lean body mass with this formula: (total body weight - lean body weight) / (total body weight) x 100.
Assume your total body weight is 123 lbs. and your lean body weight is 90 lbs. You have a body fat percentage of (123 - 90) / (123) x 100 = 26.8 percent.
Things You'll Need
- Bathroom scale
- Tape measure
- Calculator
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