Body Fat Percentage Calculator
The US Navy circumference method — surprisingly decent accuracy from nothing but a tape measure.
Estimate your body fat %
How the Navy method works
Developed for fleet-wide fitness testing, the US Navy method estimates body fat from circumference measurements — waist and neck for men, plus hips for women — and height. Validation studies put it within roughly 3–4 percentage points of lab methods for most physiques: not lab-grade, but remarkable for a $3 tape measure, and excellent for tracking change over time.
Measuring correctly (this is where accuracy lives)
Waist: at the navel, relaxed — not sucked in, not pushed out. Neck: just below the larynx, tape sloping slightly down in front. Hips (women): at the widest point. Measure in the morning, before eating, tape snug but not compressing skin, and take each measurement twice. Consistency matters more than perfection: same time, same spots, every few weeks.
Reading the number honestly
Typical reference bands (ACE): men — athletes 6–13%, fitness 14–17%, average 18–24%; women — athletes 14–20%, fitness 21–24%, average 25–31%. Women carry more essential fat by design; that's biology, not a flaw. Two cautions: single readings wobble with hydration and measurement technique, so trust the trend across weeks, and very lean targets (sub-10% men, sub-18% women) are competition territory with real hormonal costs, not year-round health goals. If you're making body-composition decisions for health reasons, loop in a doctor or dietitian.
Frequently asked questions
How accurate is this versus a DEXA scan?
DEXA is the gold standard; the Navy method typically lands within 3–4 points of it. Where it drifts: very muscular necks read leaner, and fat carried atypically can skew either way. For tracking monthly change, it's genuinely useful.
Why does my smart scale say something different?
Bioimpedance scales are highly sensitive to hydration and can swing several points in a day. Neither method is exact — pick one, use it consistently, and watch the trend rather than comparing devices.
What's a healthy body fat percentage?
Broadly: men ~10–20%, women ~18–28%, with athletic and average bands inside those. Health risk concentrates at the extremes — very high, and aggressively low maintained year-round.
How fast can body fat percentage change?
Sustainably, expect roughly 0.5–1 point per month with a moderate deficit, adequate protein, and resistance training. Faster scale loss is usually water and muscle, which defeats the purpose.