About this tool
The U.S. Navy method estimates body fat percentage from a few tape-measure circumferences — waist, neck, and (for women) hip — plus height. Developed by Hodgdon and Beckett in 1984 for military fitness assessments, it uses a logarithmic regression formula that correlates strongly with underwater weighing across large study populations, without needing calipers, scales, or lab equipment.
Because it relies on external circumference rather than a direct density or imaging measurement, it works best on people with typical fat distribution and can be less accurate for very lean athletes, bodybuilders, or people with unusual body shapes. Results below are classified into the widely-used American Council on Exercise (ACE) categories, from essential fat through athletic, fitness, average and obese ranges — but every calculator like this one is a screening estimate, not a clinical diagnosis.
Frequently asked questions
How accurate is the U.S. Navy circumference method compared to DEXA scans?
The Navy method is a convenient, no-equipment field estimate, but published validation studies generally report an error margin of roughly ±3-5 percentage points compared to gold-standard methods like DEXA (Dual-Energy X-ray Absorptiometry) or hydrostatic weighing. It's useful for tracking your own relative trend over time (are you moving in the right direction?) more than for pinpointing an exact number.
Why does the formula need my neck measurement?
The Navy method uses neck circumference as a reference point that helps normalize the waist (and hip, for women) measurement against your overall frame size — the formula was empirically derived (originally by the U.S. Navy in the 1980s) so that waist/hip circumference relative to neck circumference correlates reasonably well with body fat percentage, without needing calipers or scanning equipment. It's simply part of the validated original formula, not an arbitrary addition.