How the body fat calculator works
The main result uses the U.S. Navy method, which estimates body fat from your height and a few tape measurements: neck and waist for men, plus hip for women. It is simple to do at home and usually lands within a few percent of a DEXA scan. The calculator also shows an estimate from your BMI, age and sex for comparison.
Example: a 25-year-old man, 5 ft 10 in and 160 lb, with a 15 in neck and a 34 in waist has about 17.4% body fat, in the fitness range: 27.9 lb of fat and 132.1 lb of lean mass.
How to measure
- Neck: just below the larynx (Adam's apple), the tape sloping slightly down to the front.
- Waist: men at the navel, women at the narrowest point, after breathing out normally.
- Hip (women): around the widest part of the buttocks.
Keep the tape level and snug but not tight, and measure twice.
Why body fat matters
Two people with the same weight can have very different health risks. Fat stored around the waist is linked with heart disease and type 2 diabetes, while some fat is essential for hormones and for storing vitamins. Body fat percentage says more about health and fitness than weight or BMI alone.
Frequently asked questions
How accurate is the Navy method?
Usually within 3% to 4% of a DEXA scan when you measure carefully. It is less accurate for very lean or very heavy people.
Why do the two methods differ?
The BMI estimate only knows your height, weight, age and sex, so it can't tell muscle from fat. The tape measurements reflect where you carry fat.
What is a healthy body fat percentage?
For most adults, roughly 14% to 24% for men and 21% to 31% for women. Athletes are often lower.