Body Fat Calculator
This body fat calculator estimates the percentage of your body weight that is fat using the U.S. Navy circumference method, one of the most popular formulas you can apply at home with nothing more than a tape measure. Enter your sex, height, and a few body circumferences and it returns your body fat percentage, your fat mass and lean mass in kilograms, and the fitness category you fall into. It is a fast, no-equipment way to track changes in your body composition over time, far more informative than weight or BMI alone.
Body fat
%
Fat mass
kg
Lean mass
kg
Estimate based on the U.S. Navy circumference method. It is a statistical approximation, not a direct measurement like DEXA absorptiometry or hydrostatic weighing. Always measure with the tape snug but not tight.
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How it works
The U.S. Navy method estimates body fat from the ratio between your body circumferences and your height, because fat tends to accumulate around the waist, neck, and hips. For men it uses the neck and waist measurements; for women it adds the hip, since fat distribution differs by sex. The measurements feed a logarithmic regression formula (developed by the Naval Health Research Center) that outputs a percentage. That percentage is multiplied by your weight to split it into fat mass and lean mass. Measure the neck just below the larynx, the waist at the navel for men and at the narrowest point for women, and the hip at the widest point — accuracy depends on consistent, snug tape placement.
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Preguntas frecuentes
- What is body fat percentage?
- Body fat percentage is the share of your total body weight that is made up of fat, as opposed to muscle, bone, organs, and water. Unlike BMI, which only compares weight to height, body fat percentage distinguishes between a lean, muscular person and someone carrying excess fat at the same weight, making it a much better indicator of body composition and health.
- How accurate is the U.S. Navy method?
- The U.S. Navy circumference method is typically accurate to within about 3–4 percentage points compared with more precise techniques like DEXA scans or hydrostatic weighing. It works well for tracking changes over time when you measure consistently, but it can be less reliable at the extremes (very lean or very high body fat) and for people with unusual body proportions.
- What are healthy body fat ranges by sex?
- Using the American Council on Exercise (ACE) reference, men generally fall into: essential fat 2–5%, athletes 6–13%, fitness 14–17%, average 18–24%, and obese 25% or more. Women carry more essential fat: essential 10–13%, athletes 14–20%, fitness 21–24%, average 25–31%, and obese 32% or more.
- How should I take the measurements?
- Use a flexible tape measure and keep it snug against the skin without compressing it. Measure the neck just below the Adam's apple, the waist at the navel for men and at the narrowest point for women, and the hip at the widest part of the buttocks (women only). Take each measurement two or three times and use the average for consistency.
- Why do women need a hip measurement but men do not?
- Fat distribution differs between the sexes: women tend to store more fat around the hips and thighs, so the female formula includes the hip circumference to capture that pattern. The male formula relies on the neck and waist alone, which better reflect where men typically store fat.