Male Body Composition Calculator

Body fat (%) is estimated with the US Navy circumference method: it takes the log of (waist minus neck) and the log of height, weights them by fixed coefficients (86.010 and 70.041), and adds a constant. This is the formula Hodgdon and Beckett derived at the Naval Health Research Center in 1984 and that the Navy still uses for its official body composition assessment; the coefficients above are exactly the ones the U.S. military applies. Of the three circumference/height measurements that feed this formula, Waist circumference (cm) has by far the largest effect on the result -- roughly twice the influence of either Height (cm) or Neck circumference (cm) -- because waist is the primary driver of the (waist minus neck) term the formula is built around. A thicker neck measurement actually lowers the estimated body fat percentage, since it narrows that same waist-minus-neck gap, and a taller height also lowers the estimate, since the formula subtracts a height-weighted term. Hip circumference (cm) plays no role in Body fat (%) at all -- it's used only for Waist-to-hip ratio, a separate cardiovascular risk indicator.

Similarly, Age never enters BMI, which depends purely on Height (cm) and Weight (kg). This calculator applies a published circumference-based formula that trades some individual accuracy for convenience compared to methods like DEXA scanning or hydrostatic weighing; treat the result as a reasonable estimate, not a clinical measurement. See the U.S. Marine Corps body composition survey published by Potter et al. (2022), which restates and re-validates the exact formula and coefficients used here, for a peer-reviewed accuracy assessment against modern reference methods.