Estimate body fat with a tape measure
No scale, no calipers — the US Navy circumference method turns three or four tape measurements into a body-fat estimate.
Tools used in this guide
The job
Body-fat scales disagree wildly; DEXA is expensive. The Navy's log-circumference formula — developed for fitness standards — needs only a tape: height, neck, waist, and for women the hip too.
Measure honestly
Neck below the Adam's apple, waist at the navel standing relaxed (not sucked in), hip at the widest point. Measure in the morning — a big meal moves the waist by centimetres, and centimetres move the result.
- Men: neck + waist. Women: neck + waist + hip.
- Height 120–230 cm, tape measurements 20–300 cm.
Worked example
A man, 178 cm tall, neck 38, waist 85: the formula lands near 16.5 % — 'fitness' band. A woman at 165 cm, neck 32, waist 70, hip 95 comes out near 25 % — the top edge of 'fitness'.
Where it stops
A screening estimate, ±3–4 points against real measurement. It can output impossible values (under ~1 % or over ~70 %) when tape numbers are odd — that is the formula being extrapolated, not a diagnosis.