Body Fat Calculator
This body fat calculator estimates what share of your weight is fat. With a tape measure, it uses the US Navy circumference method (neck and waist, plus hips for women). Without one, it gives a rougher estimate from your BMI, age and sex. You also see your fat mass and lean mass in pounds and a fitness category, so you can track changes over time.
Updated
Results
- CategoryAmerican Council on Exercise chart
- Fat mass
- Lean massEverything that isn’t fat
- BMI (kg/m²)
Results are estimates. See the methodology below.
How to use the body fat calculator
- Choose your sex and the method: US Navy (tape measure) or BMI (no tape needed).
- Enter your age, weight in pounds and height in inches (5 ft 10 in = 70 in).
- For the Navy method, enter your neck and waist; women also enter their hips. Half-inch precision is enough.
- Read your body fat percentage, category, fat mass, lean mass and BMI.
How to measure
The steps below follow the military tape-test protocol (US Coast Guard desk guide). Use a flexible, non-stretch tape, stand relaxed with arms at your sides, keep the tape level and snug without compressing the skin, and read it at the end of a normal breath out.
- Neck: just below the Adam’s apple (larynx), with the tape at a right angle to the neck.
- Waist, men: around the abdomen at the level of the navel.
- Waist, women: at the natural waist, the narrowest point, usually about halfway between the navel and the bottom of the breastbone.
- Hips, women: around the widest part of the buttocks, as seen from the side.
The official protocol takes each measurement three times; doing the same at home makes your result more repeatable.
Formulas used
US Navy method
Developed by Hodgdon and Beckett at the Naval Health Research Center (1984). With all measurements converted to centimeters:
Men: 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450
Women: 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450
BMI method
Deurenberg and colleagues (1991) estimate body fat from BMI: 1.2 × BMI + 0.23 × age − 10.8 × sex − 5.4, where sex is 1 for men and 0 for women.
Fat mass, lean mass and categories
Fat mass = weight × body fat %. Lean mass is the rest (muscle, bone, organs, water). The category uses the American Council on Exercise (ACE) chart:
| Category | Women | Men |
|---|---|---|
| Essential fat | 10–13% | 2–5% |
| Athletes | 14–20% | 6–13% |
| Fitness | 21–24% | 14–17% |
| Average | 25–31% | 18–24% |
| Obese | 32% and up | 25% and up |
Examples
Man, 40, 5 ft 10 in, 190 lb, neck 15 in, waist 36 in
The Navy method gives 21.1% body fat, in the average range: 40.1 lb of fat and 149.9 lb of lean mass. His BMI is 27.3. The BMI method puts the same man at 25.7%, in the obese range, which shows how far the two estimates can differ.
Woman, 35, 5 ft 6 in, 145 lb, neck 13 in, waist 30 in, hips 38.5 in
Navy result: 28.2%, average, with 40.9 lb of fat and 104.1 lb of lean mass (BMI 23.4). Using BMI alone gives 30.7%.
How accurate is it?
Both methods are estimates. The Navy formula relies on a few circumferences, so a half-inch error at the waist changes the result. The BMI method knows nothing about muscle and tends to misjudge very muscular people. Lab methods such as DEXA, air displacement (Bod Pod) and underwater weighing are more accurate but cost more; skinfold calipers depend on finding the exact site, and bioelectrical impedance scales are affected by how hydrated you are.
For tracking, consistency beats precision: measure at the same time of day, with the same tape and method, every few weeks.
This calculator is for adults. Results are not meaningful during pregnancy. If your number worries you, or if you have or have had an eating disorder, talk to your doctor or a registered dietitian rather than chasing a lower percentage.
Frequently asked questions
What is a healthy body fat percentage?
On the ACE chart, the fitness range is 21–24% for women and 14–17% for men, and average is 25–31% and 18–24%. Women naturally carry more essential fat than men.
Is the Navy body fat calculator accurate?
It is a practical field method, not a lab measurement. Careful, repeated measurements give a useful estimate and a good way to track change, but your true value can be higher or lower.
Why do the Navy and BMI methods give different results?
The BMI method only knows weight, height, age and sex, so a heavier, muscular person looks fatter than they are. The Navy method uses your waist, which reflects abdominal fat more directly.
Where do I measure my waist?
Men measure at the navel. Women measure at the natural waist, the narrowest point between the navel and the bottom of the breastbone. Keep the tape level and read it after a normal exhale.
What is lean body mass?
Everything that is not fat: muscle, bone, organs and water. In the first example above, 190 lb at 21.1% body fat leaves 149.9 lb of lean mass.
Can I use this calculator for teenagers?
No. It accepts ages 18 and up, and the formulas and categories were built for adults. A pediatrician can assess a child’s or teen’s growth and body composition.
Sources
This calculator gives an estimate for adults and is not a medical measurement or diagnosis. For questions about your weight or health, talk to your doctor or a registered dietitian.