Tape relaxed, don't suck in. It's an estimate — the trend over weeks matters more than any single reading.
How the Navy tape test works
The U.S. military needed a body-fat check that any unit could run with a tape measure — fast, cheap, repeatable. The Navy circumference method estimates body density from a few girth measurements and converts it to a body-fat percentage:
Men: 495 / (1.0324 − 0.19077×log₁₀(waist−neck) + 0.15456×log₁₀(height)) − 450
Women add the hip measurement, because fat distribution differs. It's the same math behind the tape test I stood for twice a year for eight years in the Marine Corps.
How to measure correctly
Neck: just below the Adam's apple, tape sloped slightly down at the front. Waist: at the navel for men, at the narrowest point for women — relaxed, at the end of a normal exhale, no sucking in. Hips (women): at the widest point. Measure on bare skin, keep the tape level, take each measurement twice and average.
What the ranges mean
For men: 6–13% reads athlete, 14–17% fit, 18–24% average, 25%+ above average. For women, add roughly 8–10 points to each band — essential fat is simply higher. Health and performance live in a range, not at a single number; where you hold steady while training hard and eating well matters more than chasing a stage number year-round.
FAQ
How accurate is the Navy body-fat method?
Typically within 3–4% of DEXA for most physiques. Build affects it — a thicker neck lowers the estimate and a blockier midsection raises it — so use it as a consistent trend tool, not a lab result.
Is this the same test the military actually uses?
Yes — the circumference method is the DoD standard for body-composition assessment, with minor service-specific variations in where and how many times they measure.
How often should I measure?
Every 2–4 weeks, same time of day, same conditions. Week-to-week water shifts create noise; the monthly trend is the signal.
What's a realistic rate of body-fat loss?
Around 0.5–1% of body weight per week of scale loss, which typically works out to 1–2 body-fat points per month early on, slowing as you lean out.