Most people use their body mass index, or BMI, to calculate their body fat percentage. A BMI doesn't measure your actual body fat -- it estimates your body fat based on a calculated ratio of your height to your weight. According to the Centers for Disease Control and Prevention, your BMI is a "fairly reliable indicator of body fatness for most people." But if you have a high percentage of muscle mass, your BMI may not be accurate. Also, women tend to have a higher body-fat percentage than men at the same height and weight, and older people tend to have more body fat than younger people at the same height and weight.
Step 1
Start by calculating your BMI. Although it may not be the most accurate way to determine body fat percentage, it's a good place to begin. BMI calculators are available online -- you'll simply need to know your weight in pounds and your height in inches. If you'd like to do the math yourself, divide your weight in pounds by your height in inches squared. Multiply that number by 703. A BMI below 18.5 is underweight. Normal BMI ranges from 18.5 to 24.9; the overweight range is between 25 and 29.9; and a BMI over 30 is considered obese.
Step 2
Measure your body fat using the caliper method. Also called a skin-fold test, you'll need someone to measure the amount of excess skin you can pinch between specially calibrated calipers at specific body sites -- the chest, below the armpit, bicep, tricep, below the scapula, stomach, hip, lower back, thigh and calf. Each measurement is then multiplied by its own unique factor. Then results are added or multiplied to achieve a final result. It's a complicated formula, but you can also simply plug your results into an online calculator and the work is done for you. Results should be accurate within 2 percent, but human error in the measuring process can cause inaccurate results.
Step 3
Have a dual energy X-ray absorptiometry test performed. Called DEXA, it's a body-scanning test that precisely measures muscle, body fat and bone density. The test takes about 10 minutes and may cost up to $300 but is the most accurate and most convenient method to know your body-fat percentage.
Tips and Warnings
- Your body-fat percentage may be a more accurate measure than just your weight or BMI for your risk of disease. At a healthy weight, women should have a higher body-fat percentage than men. Fit men should have a fat percentage between 14 and 17 percent; fit women will be between 21 and 24 percent.
- Don't focus on losing weight -- focus on building lean muscle mass and losing fat, which is a much better indication of health than weight alone.
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