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Navy Body Fat Calculator (Hodgdon-Beckett method)
Estimate your body-fat percentage with the US Navy (Hodgdon-Beckett) circumference method — the general body-fat standard used across the fitness world. For men the formula is %BF = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76; women add hip circumference, using waist + hip − neck. All measurements are in inches (centimetres convert automatically). For a man with a 36-inch waist, 16-inch neck and 70-inch height that works out to about 19.4%: 86.010 × log10(20) − 70.041 × log10(70) + 36.76 = 111.90 − 129.24 + 36.76. Alongside the percentage you get your fat-mass and lean-mass split in kilograms, an FFMI reading scored against the roughly 25 natural ceiling, and your body-fat category by sex. The Navy method is convenient but only an estimate — it carries a small bias and runs about ±3–4% versus a DEXA scan, so use DEXA or professionally administered calipers when you need precision. General fitness guidance.
US Navy man: 86.010·log₁₀(waist−neck) − 70.041·log₁₀(height) + 36.76
- Waist 36″, neck 16″, height 70″ → ≈ 19.4% body fat (Average)
- Women add hip: waist + hip − neck
Frequently asked questions
How does the Navy body fat calculator work?
It uses tape measurements of your neck, waist (and hip for women) plus your height. For men, %BF = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76; women use waist + hip − neck with different constants. It is the Hodgdon-Beckett method developed by the Naval Health Research Center, and all measurements are in inches.
How accurate is the Navy body fat method?
It is a good estimate but not a measurement. The Navy circumference method carries a small bias (roughly −2.6% in men, +2.3% in women) and runs about ±3–4% versus a DEXA scan, the practical reference standard. For a precise figure, use DEXA or professionally administered skinfold calipers.