ToolPilot
Body fat calculator
US Navy method from circumference measurements. Men: height, waist (at navel), neck. Women: same plus hip. Add weight to estimate fat mass and lean mass. Switch between centimetres and inches.
Measurements
Results
Estimated body fat
20.8%
Category: Average
Bands are common reference ranges (essential / athletes / fitness / average / obese) and vary by source.
Fat mass
15.6 kg
Lean mass
59.4 kg
How it works
The US Navy estimates body density from circumferences, then maps to body fat %. All terms in the published equation use the same length unit—here we use inches internally (centimetres are converted). Men: 86.010×log₁₀(waist−neck) − 70.041×log₁₀(height) + 36.76. Women add hip: 163.205×log₁₀(waist+hip−neck) − 97.684×log₁₀(height) − 78.387. Fat mass and lean mass apply your entered weight to that percentage.
FAQ
How accurate is the US Navy method?
It correlates reasonably with lab methods for many people but can be off if measurements are inconsistent, if you are very muscular, or if body shape differs from the populations used to build the equations.
Where exactly should I measure?
Waist is at the navel with a horizontal tape; neck is just below the larynx, sloping slightly down. Hip (women) is the widest part of the hips/buttocks. Keep the tape snug but not compressing skin.
Why must waist be larger than neck (men)?
The male formula uses log₁₀(waist − neck). If waist ≤ neck, the math is invalid or meaningless—usually a sign of wrong units or mis-measurement.
Do categories replace medical advice?
No. Categories are simplified labels. Health risk depends on many factors; use this tool for awareness and discuss goals with a qualified professional if needed.