About this calculator
The US Navy body fat method uses tape measurements (neck, waist, hip for women) and height to estimate body fat percentage. Developed by Hodgdon and Beckett in 1984, it’s accurate within ±3–4% compared to DEXA scans — good enough for tracking trends, not great for absolute precision.
The formula
Men: BF% = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76
Women: BF% = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387
All in centimeters. The calculator handles imperial/metric conversion.
How to measure correctly
- Neck — just below the larynx, tape level all the way around. Don’t flex.
- Waist (men) — at the navel.
- Waist (women) — at the natural waist (narrowest point, usually 1–2" above navel).
- Hip (women) — at the widest point, typically at the greater trochanters.
- Measure first thing in the morning, before eating or drinking, after using the bathroom. Consistency matters more than absolute accuracy for tracking.
Body fat categories
Men: essential 2–5%, athletic 6–13%, fit 14–17%, average 18–24%, above average 25%+. Women: essential 10–13%, athletic 14–20%, fit 21–24%, average 25–31%, above average 32%+. Note women always need higher body fat for hormonal function — comparing across sexes is meaningless.
When to use this vs other methods
- Navy tape (this) — Free, repeatable, ±3–4%. Good for tracking.
- BIA scales — $30–200, ±5–8%. Daily variation high (hydration). Useful for trends.
- Calipers — $10–50, ±3–5% with practice. Operator-dependent.
- DEXA scan — $50–150 per scan, ±1–2%. The gold standard. Worth doing once or twice to calibrate your other methods.
- BodPod / hydrostatic weighing — $30–100, ±2–3%. Accurate but inconvenient.