DIY Cost Tools
Body Fat Calculator
HEALTH CALCULATOR
Estimate adult body-fat percentage from height and circumference measurements using a Navy-style equation.
How it works
The circumference equation combines height with neck and waist measurements; the female equation also includes hip circumference. Weight is used only to estimate fat and lean mass.
Formula
The method applies sex-specific logarithmic circumference equations. Estimated fat mass = body weight × estimated percentage.
Worked example
For the default male measurements—180 cm tall, 40 cm neck, 90 cm waist, and 80 kg—the calculator produces a body-fat estimate and corresponding mass breakdown.
Important limits
- Circumference placement, tape tension, hydration, and body shape can materially affect results.
- This is a screening estimate, not a diagnosis or a direct body-composition measurement.
- The equation’s sex categories and validation samples do not represent every person.
Frequently asked questions
Why can this differ from a smart scale?
Different methods use different assumptions and error sources. Track trends using the same method and conditions.
Should I use the result to make medical decisions?
No. Discuss concerning changes or health risks with a qualified healthcare professional.
Sources and review notes
The calculator uses a circumference method associated with U.S. Navy body-composition research; published validation shows prediction error is possible. Treat the result as an estimate. Last reviewed September 29, 2026.