Body Fat Calculator
How it works
US Navy method: uses your neck and waist (plus hips for women) against your height in a published circumference formula. It reflects where you carry fat, so it’s usually within a few points of a DEXA scan.
BMI method (Deurenberg): estimates body fat from your BMI and age — convenient with no tape measure, but less precise because BMI can’t tell muscle from fat. Lean body mass is your weight minus your estimated fat mass.
Both formulas are fully published and verifiable — we don’t use hidden proprietary coefficients. Treat any single estimate as a guide and track the trend over time.
Frequently asked questions
How is body fat percentage calculated?+
This calculator offers two methods you can choose between: the US Navy circumference method, which uses your neck, waist (and hip for women) measurements, and the Deurenberg method, which estimates body fat from your BMI and age. Both are published, verifiable formulas.
Which body-fat method is more accurate?+
The US Navy tape method is generally more accurate because it reflects where you carry fat, and is often within a few points of a DEXA scan. The BMI-based estimate is more convenient but less precise, since it can't tell muscle from fat.
How do I measure my waist and neck correctly?+
Measure your neck just below the larynx, and your waist at the navel while relaxed (don't suck in). Women also measure the hips at their widest point. Use a flexible tape held snug but not tight.
What is a healthy body fat percentage?+
Rough fitness ranges are about 14–24% for men and 21–31% for women; athletes sit lower. Below roughly 6% (men) or 14% (women) is essential fat and hard to sustain.
What is lean body mass?+
Lean body mass is everything that isn't fat — muscle, bone, organs and water. We calculate it as your weight minus your fat mass, which is useful for setting protein targets and tracking recomposition.