Body Fat Calculator
Estimate your body-fat percentage with just a tape measure, using the U.S. Navy circumference method (Hodgdon–Beckett) — and see which fitness band you land in.
16.4% is a lean, healthy "fitness" level for men — a sustainable place for most active people.
Educational estimate, not medical advice. The Navy method’s standard error is ~3–4% body fat vs hydrostatic weighing — great for tracking a trend, not a precise clinical value. Measure relaxed at the end of a normal breath, same conditions each time. DEXA or a Bod Pod are more accurate if you need an exact figure.
Track the trend, not the noise
ONDA Life logs measurements like this over time and ties them to your training, sleep and recovery — so you can see whether your plan is actually working.
Download ONDA Life on the App Store →Sources & methodology
This uses the U.S. Navy circumference method (Hodgdon & Beckett, 1984) — a tape measure only, no calipers or scale. It estimates body fat from the log of your waist (and hip, for women) minus neck, against height. The published standard error is roughly 3–4% body fat versus hydrostatic (underwater) weighing, so it is reliable for tracking a trend over weeks but not a precise clinical figure; methods like DEXA or air-displacement plethysmography are more accurate. Measure relaxed, at the end of a normal breath: waist at the navel (men) or the narrowest point (women), neck below the larynx, hips at the widest point. Category bands follow common ACE fitness cut-offs. Educational only, not medical advice.
- [1] Hodgdon JA, Beckett MB (1984). Prediction of percent body fat for U.S. Navy men from body circumferences and height (Report 84-11). Naval Health Research Center, San Diego, CA.
The men’s circumference equation used here (waist, neck, height).
- [2] Hodgdon JA, Beckett MB (1984). Prediction of percent body fat for U.S. Navy women from body circumferences and height (Report 84-29). Naval Health Research Center, San Diego, CA.
The women’s circumference equation (waist, hip, neck, height).
Common questions
Where do these body-fat numbers come from?
The estimate uses the U.S. Navy circumference equations developed by Hodgdon & Beckett at the Naval Health Research Center in 1984 (Reports 84-11 for men and 84-29 for women). Full citations are in the Sources section on this page. Category labels follow common ACE fitness ranges.
How accurate is the Navy body-fat method?
It has a standard error of about 3–4% body fat compared with hydrostatic weighing — good enough to track changes over time with a tape measure, but not a precise clinical value. DEXA, hydrostatic weighing and air-displacement plethysmography (Bod Pod) are more accurate; skinfold calipers are similar in error to this method when done well.
How do I measure correctly?
Use a flexible tape, snug but not compressing, relaxed and at the end of a normal exhale. Neck: just below the larynx. Waist: at the navel for men, at the narrowest point for women. Hips (women): at the widest point of the buttocks. Take each measurement twice and average them, and measure under the same conditions each time for consistent trends.
What is a healthy body-fat percentage?
Rough ACE ranges: for men, ~6–13% is athletic, 14–17% fitness, 18–24% average; for women, ~14–20% athletic, 21–24% fitness, 25–31% average. Essential fat (the minimum for health) is about 2–5% in men and 10–13% in women. "Healthy" varies with age, genetics and goals — the trend matters more than a single number.
Why does the women’s formula need a hip measurement?
Women carry proportionally more fat around the hips, so the equation Hodgdon & Beckett fitted for women includes hip circumference alongside waist and neck to predict body fat accurately. The men’s equation uses only waist and neck against height.