Body Fat % — Quick 8‑Section Guide
Estimate body‑fat percentage using the U.S. Navy tape method and a BMI‑based estimate. Inputs work in metric or US units; math runs locally.
1) Core idea
- U.S. Navy: uses neck, waist, height (plus hip for females)
- BMI method: 1.20×BMI + 0.23×Age − 16.2 (men) or − 5.4 (women)
2) Flow
- Select units and gender; enter measurements
- Exact conversions: 1 in = 2.54 cm; 1 lb = 0.45359237 kg
- We compute Navy BFP, BMI, BMI‑BFP, fat mass, and lean mass
3) Sanity checks
- Use relaxed, consistent tape tension
- Measure waist at navel level; neck just below larynx
4) Shortcuts
- Take 2–3 readings and average them
- Use the same time of day to reduce water‑weight noise
5) Pitfalls
- BMI‑based estimate can overstate BFP in lean/muscular people
- Tape placement drift causes inconsistent results
6) Micro examples
- Male (US): neck 15 in, waist 32 in, height 67 in → Navy ≈ 17%
- Female adds hip: use waist + hip − neck in the formula
7) Mini‑FAQ
- Which is better? Navy is practical; DEXA is the gold standard
- Privacy? All calculations run in your browser
8) Action tip
Track BFP monthly with consistent technique; pair with waist and weight trends to guide diet/training.