Body Fat Calculator
The US Navy circumference method — a tape measure and two or three honest measurements. Not lab-grade, but consistent enough to track direction if you measure the same way every time.
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The equations (Hodgdon & Beckett 1984, all in cm): men — %BF = 495 ÷ (1.0324 − 0.19077×log₁₀(waist − neck) + 0.15456×log₁₀(height)) − 450. Women — %BF = 495 ÷ (1.29579 − 0.35004×log₁₀(waist + hip − neck) + 0.22100×log₁₀(height)) − 450. Developed at the Naval Health Research Center against hydrostatic weighing.
Honesty about error: a tape method carries meaningful individual error versus lab methods — tape tension, time of day and where exactly you measure all move the number. Its real value is the trend: measure fortnightly, same morning, same spots, and watch the direction rather than worshipping any single reading.
These are population formulas — a starting point, not a prescription. Your training history, sleep, stress and cycle shift the real answer. That is what the 9-axis Body Scan measures.
Sources
- Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men and women from body circumferences and height. Reports No. 84-11 and 84-29. San Diego, CA: Naval Health Research Center; 1984.
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