Body Fat Calculator — Navy Method & Lean Mass
Estimate body fat from neck, waist, hip, and height measurements, then explore fat mass, lean mass, and a target-weight scenario in metric or US units.
Body composition estimate
Keep the tape level and snug without compressing skin.
Measurements
Weight is optional but enables fat mass, lean mass, and target estimates.
Where to measure
Body composition
Estimate details
How the calculator works
It applies the sex-specific circumference equations published in Army Regulation 600-9. Metric inputs are converted to inches before evaluating the base-10 logarithm formula.
How to measure
Stand relaxed. Measure the neck just below the larynx and waist at the navel. The female equation also uses hips at the widest point.
Fat mass and lean mass
With weight entered, fat mass equals weight multiplied by the estimated percentage. Lean mass is the remainder.
Target scenario
Target weight assumes lean mass stays unchanged. Real change can include muscle and water, so this is not a prescription.
Frequently asked questions
Is the Navy circumference method exact?
No. It is a practical field estimate affected by technique, tape placement, and body shape.
Can I use centimeters?
Yes. The calculator converts centimeters to inches internally.
Why does the female equation use hips?
Its circumference value is waist plus hip minus neck; the male equation uses waist minus neck.
Is target weight medical advice?
No. It is a mathematical scenario assuming constant lean mass.
