Body Fat & Lean Mass Calculator
Estimate your body-fat percentage, fat mass, and lean body mass with the U.S. Navy method. Free, no signup.
About 18.4% body fat, which is 69.4 kg of lean mass. This is a Navy-method estimate — track the trend over weeks rather than any single reading.
Feed your lean mass into the TDEE and protein tools for targets that are more accurate than scale weight.
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About this calculator
The U.S. Navy method estimates body-fat percentage from a handful of tape-measure circumferences — neck and waist for men, plus hips for women — together with your height. It’s not as precise as a DEXA scan, but it’s free, repeatable at home, and accurate enough to track a trend over weeks. From body-fat percentage we derive your lean body mass (everything that isn’t fat) and fat mass. Lean body mass is the number that sharpens the rest of your plan: the calorie calculator can switch to the Katch-McArdle equation with it, and protein targets are best set from lean mass rather than scale weight. Measure relaxed, at the same time of day, tape snug but not compressing the skin.
Sources
U.S. Navy circumference method (Hodgdon & Beckett, 1984). Body fat is an estimate; DEXA or calipers are more accurate.
FAQs
How accurate is the Navy method?
Typically within about 3–4 percentage points of a DEXA scan for most people, and reliable for tracking change over time as long as you measure consistently. It can be off for very lean or very heavy individuals. Use it for trends, not a single definitive number.
Where exactly do I measure?
Neck: just below the larynx, tape sloping slightly down at the front. Waist: at the navel for men, at the narrowest point for women. Hips (women): at the widest point of the glutes. Keep the tape level and snug.
Why does it feed my calorie and protein targets?
Lean body mass drives energy expenditure and protein needs more than total weight does. With a body-fat figure, the TDEE calculator can use Katch-McArdle and the protein calculator can target grams per kg of lean mass — both more accurate for muscular athletes.