Quick answer
How is body fat percentage calculated?
The US Navy body fat method uses your height, neck and waist (plus hips for women) in a logarithmic formula. A man 175 cm tall with a 38 cm neck and 86 cm waist has about 17.8% body fat, which falls in the “fitness” range. Healthy ranges are roughly 14–24% for men and 21–31% for women.
- Men: 86.010 × log(waist − neck) − 70.041 × log(height) + 36.76
- Women: 163.205 × log(waist + hip − neck) − 97.684 × log(height) − 78.387
- Measurements in inches; the calculator converts cm for you
How do you take measurements for the body fat calculator?
You need a soft, non-stretch tape. Keep it flat and snug, breathe out normally and don’t pull your stomach in.
- Height: stand straight against a wall without shoes.
- Neck: just below the Adam’s apple, with the tape sloping slightly down at the front.
- Waist: at the navel for men, and at the narrowest part of the waist for women.
- Hips (women): around the widest part of the hips and buttocks.
Enter each measurement in centimetres or inches. Take each one twice and use the average.
How is body fat percentage calculated?
The US Navy tape method puts your measurements into a logarithmic formula, in inches. Men use waist minus neck. Women use waist plus hips minus neck, because women tend to carry more fat on the hips.
Take a woman who is 160 cm tall with a 32 cm neck, 74 cm waist and 96 cm hips. Her body fat comes out at about 29.0%, in the average range. If she weighs 58 kg, her fat mass is about 16.8 kg and her lean mass about 41.2 kg.
The waist matters most. For a man 170 cm tall with a 37 cm neck, a 92 cm waist gives about 23.8% body fat. Bring the waist down to 88 cm and it drops to about 20.9%.
What is a healthy body fat percentage?
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese | 25% + | 32% + |
A body fat calculator gives an estimate, usually within 3–4 percentage points of a lab scan. It is best for tracking change over time. If your result is in the obese range, or you are worried about your weight, talk to your doctor.
Frequently asked questions
How do I measure body fat at home?
Use a tape measure and the US Navy method: measure your height, neck (just below the larynx) and waist (at the navel for men). Women also measure the widest part of the hips. Enter them above to get your body fat percentage.
What is a healthy body fat percentage?
For men, about 14–24% is typical and 6–13% is athletic. For women, about 21–31% is typical and 14–20% is athletic. Above 25% for men or 32% for women is classed as obese.
How accurate is the US Navy body fat method?
It’s usually within about 3–4 percentage points of lab methods like DEXA, which is good enough to track changes over time if you measure the same way each time.
Is body fat better than BMI?
Body fat percentage shows how much of your weight is fat, so it handles muscular people better than BMI. Using both, plus waist size, gives the fullest picture.
Can I enter my measurements in inches?
Yes. Switch the unit to inches and the values convert automatically. The US Navy formula itself works in inches, so centimetres are divided by 2.54 before the calculation.
Why do I need my weight for the body fat calculator?
Weight isn’t needed for the body fat percentage, which comes only from your height, neck, waist and hip measurements. Adding it lets the calculator split your weight into fat mass and lean mass, for example 12.8 kg of fat at 72 kg and 17.8%.