Below the larynx
At the navel
Used to estimate fat mass and lean mass
Men: Essential 2–5% · Athletes 6–13% · Fitness 14–17% · Average 18–24% · Obese 25%+
How to use the Body Fat Calculator
- 1Select your sex and choose Metric or Imperial units.
- 2Enter your height.
- 3Measure and enter your neck and waist circumference, plus your hip circumference if you are female.
- 4Optionally enter your weight to calculate fat mass and lean mass.
- 5Read your estimated body fat percentage and its ACE category.
How to take your measurements
Use a flexible, non-stretch tape and measure on bare skin. Keep the tape level and snug without compressing the skin, and take each measurement two or three times, using the average. Measure in the morning before eating for the most consistent results.
Measure the neck just below the larynx (Adam's apple), with the tape sloping slightly downward toward the front. Men measure the waist horizontally at the level of the navel; women measure it at the narrowest point of the torso. Women also measure the hips at the widest point of the buttocks. Stand relaxed and do not pull your stomach in.
The U.S. Navy body fat formula
The Navy method estimates body density from circumferences and height, then converts it to a body fat percentage. With measurements in centimeters, the formula for men is 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450. For women it is 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450. Imperial measurements are converted to centimeters first.
For example, a man who is 180 cm tall with a 39 cm neck and a 90 cm waist has an estimated body fat of about 19.1%. If he weighs 80 kg, that is roughly 15.3 kg of fat mass and 64.7 kg of lean mass. A woman who is 165 cm tall with a 34 cm neck, 76 cm waist and 100 cm hips comes out at about 29.4%.
Body fat percentage categories
The calculator uses the categories published by the American Council on Exercise (ACE). For men: essential fat 2–5%, athletes 6–13%, fitness 14–17%, average 18–24% and obese 25% or more. For women: essential fat 10–13%, athletes 14–20%, fitness 21–24%, average 25–31% and obese 32% or more. Both examples above fall in the average range.
Women naturally carry more essential fat than men, which is why their ranges are higher. Essential fat is needed for normal hormone and organ function, so going below it is not a healthy goal. Body fat percentage adds useful context to the BMI calculator, which cannot tell fat from muscle.
How accurate is the Navy method?
Tape-based formulas are practical and free, but they are estimates. Compared with lab methods such as DEXA scans, the Navy method is often within a few percentage points, though errors can be larger for very lean, very muscular or very heavy people. Small measuring errors matter: a waist reading that is just 1 cm off can shift the result by about half to three-quarters of a percentage point.
The best use is to track change over time with the same tape, technique and time of day. If you are trying to lose fat while keeping muscle, combine regular measurements with a sensible eating plan from the calorie calculator.
Learn more
Frequently asked questions
What is a healthy body fat percentage?
By the ACE categories, roughly 14–24% for men and 21–31% for women covers the fitness and average ranges. Athletes are often lower, and values in the obese range (25%+ for men, 32%+ for women) are linked with higher health risks.
Why do women need a hip measurement?
Women tend to store more fat around the hips and thighs, so the female version of the Navy formula includes hip circumference to capture that. The male formula only needs the neck and waist.
Do I need to enter my weight?
No. Body fat percentage is calculated from height and circumferences alone. Weight is only used to split your total weight into fat mass and lean mass.
Can I measure in inches?
Yes. Switch to Imperial and enter height in feet and inches and circumferences in inches. If you need to convert a measurement for another purpose, use the length converter.
Why does my result change from day to day?
Your waist size can vary with meals, bloating and hydration, and small differences in where you place the tape add up. Measure under the same conditions each time and look at the trend over several weeks.