Body Fat Calculator
Estimate body-fat percentage from tape measurements with the US Navy method.
How it works
Men: BF% = 495 ÷ (1.0324 − 0.19077·log₁₀(waist−neck) + 0.15456·log₁₀(height)) − 450
The US Navy circumference method: girth measurements stand in for body density. Measure with a flexible tape, snug but not compressing, and take each site twice. Accuracy is typically within ±3–4% of lab methods.
Worked example
A man 69 in tall, 34-in waist, 15-in neck: BF ≈ 495 ÷ (1.0324 − 0.19077·log₁₀(19) + 0.15456·log₁₀(69)) − 450 ≈ 18%.
Frequently asked questions
How accurate is the tape method?
Within a few percent for most physiques, and very consistent for tracking change if you measure the same way each time. Unusual fat distributions read less accurately.
When should I measure?
Morning, before food and water, tape parallel to the floor. Consistency beats precision.
What body fat should I aim for?
The "fitness" bands — roughly 14–17% for men and 21–24% for women — balance looks, health and sustainability for most people.
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This is a general educational estimate, not medical advice. Bodies differ — for decisions about diet, training, medication or health conditions, talk to a doctor or registered dietitian.