Body Fat Calculator (Navy Method)
Tape measurements in, fat percentage out — with the honest ±3% caveat.
How this is calculated
Men: 495 ⁄ (1.0324 − 0.19077·log₁₀(waist−neck) + 0.15456·log₁₀(height)) − 450
Women add the hip measurement inside the first logarithm. Worked example: male, 180 cm, neck 38, waist 85 → about 15% — the fit band. The tape cannot see where your fat actually sits, which is why the honest claim is direction-tracking within ±3%, not lab precision. For clinical numbers, a DEXA scan is the reference. Not medical advice.
Frequently asked questions
How does the Navy body fat method work?
From a height plus tape measurements — neck and waist for men; neck, waist, and hip for women — plugged into the US Navy’s logarithmic formula. It estimates the body density those circumferences typically imply, then converts to a fat percentage.
How accurate is a tape-measure estimate?
Within roughly ±3% for most people when measured carefully — genuinely useful for tracking direction over months, less meaningful as a single absolute number. Measure at the same time of day, tape level and snug but not compressing, and average two readings.
Where exactly do I measure?
Neck: just below the larynx, tape sloping slightly down at the front. Waist: men at the navel; women at the narrowest point. Hips (women): the widest point around the glutes. Relaxed, not sucked in — honest tape, honest number.
What are typical body fat ranges?
Rough adult bands: athletic men ~6–13%, fit 14–17%, average 18–24%; athletic women ~14–20%, fit 21–24%, average 25–31%. Essential fat sits near 3–5% (men) and 10–13% (women) — going below is a medical situation, not a fitness goal. Not medical advice.