About BodyFatMath

BodyFatMath is composition arithmetic: what percentage of you is fat by the Navy method, how much is lean mass, and whether your fat is distributed where risk lives.

BodyFatMath exists because the scale cannot tell fat from muscle and BMI cannot see distribution. The circumference methods are old, validated, and free — and they answer the questions the bathroom scale cannot.

Every calculator on BodyFatMath shows its formula and its assumptions on the page, so you can check the math, reproduce it in a spreadsheet, or argue with it. Inputs are processed entirely in your browser — nothing is sent to a server, and there are no accounts.

BodyFatMath is an independent, ad-supported project. We are not affiliated with any lender, brand, agency, or the sources we cite (NIH and CDC public guidance). If a number looks wrong, the contact page reaches a human who fixes it.

What makes BodyFatMath different

• Your numbers never leave your browser. Every calculator on BodyFatMath runs entirely on your device. We never see, store, or transmit the figures you enter — there are no accounts and no server-side processing of your inputs.
• Published methodology. Each calculator page explains the exact formula it uses and the assumptions behind it, so you can check our work or reproduce it in a spreadsheet.
• Free, forever, without a paywall. BodyFatMath is supported by advertising. There is no premium tier, no email gate, and no upsell.

Independence

BodyFatMath is an independent educational project. We are not affiliated with, endorsed by, or acting on behalf of any government agency, lender, insurer, or the organizations whose formulas and public data we reference (such as NIH and CDC public guidance). All trademarks and referenced standards belong to their respective owners.

Questions, corrections, or suggestions are genuinely welcome — get in touch.