Body Fat Calculator
Estimate body fat percentage from tape measurements using the US Navy method, with body-fat category, fat mass and lean body mass.
Body fat
17.4%
Fat mass
30.7 lb
Lean body mass
145.3 lb
The US Navy tape method estimates body fat from body circumferences; it is typically within 3–4 percentage points of a DEXA scan and can be off more for very lean or very heavy builds. Measure relaxed, without holding your breath, and keep the tape level. This is a fitness estimate, not a medical measurement.
Estimating body fat with the US Navy method
The US Navy circumference method estimates body fat percentage from a few tape measurements — height, neck, and waist for men, plus hip for women — using a formula fitted to hydrostatic-weighing data. It works because fat distributes in predictable places: a larger waist relative to neck and height signals a higher fat percentage. No calipers, scales, or scans are needed.
Once body fat percentage is known, splitting body weight into fat mass and lean body mass is simple: fat mass is weight × body-fat %, and lean mass (muscle, bone, organs, water) is the remainder. Tracking lean mass over time is useful when dieting — the goal is usually to lose fat mass while holding lean mass roughly steady.
Accuracy: the Navy method is typically within 3–4 percentage points of a DEXA scan for people of average build, and less accurate at the extremes — very lean athletes and people carrying a lot of fat. Measurement technique is the main source of error. Measure at the same time of day, tape snug but not compressing the skin, level around the body, and relaxed (do not suck in). Take each measurement twice and average.
Category ranges differ by sex because women carry more essential fat. Rough bands: for men, 2–5% essential, 6–13% athletic, 14–17% fitness, 18–24% average, 25%+ above average; for women, add roughly 8–10 points to each band. These are general references, not clinical thresholds — use the trend, not a single reading, and consult a professional for a body-composition assessment.
Key formulas (reference)
All measurements in centimetres. men: %fat = 495 / (1.0324 − 0.19077·log10(waist − neck) + 0.15456·log10(height)) − 450 women: %fat = 495 / (1.29579 − 0.35004·log10(waist + hip − neck) + 0.22100·log10(height)) − 450 Fat mass = weight × %fat ; Lean mass = weight − fat mass
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Frequently Asked Questions
How does the US Navy body fat method work?
It estimates body fat percentage from tape measurements — height, neck and waist for men, plus hip for women — using a formula fitted to hydrostatic weighing data. A larger waist relative to neck and height indicates a higher fat percentage. No calipers or scans are needed.
How accurate is it?
For people of average build it's typically within 3–4 percentage points of a DEXA scan. It's less accurate for very lean athletes and for people carrying a lot of fat. Measurement technique is the main source of error, so measure carefully and average two readings.
How should I take the measurements?
Use a flexible tape, snug against the skin but not compressing it, kept level around the body. Measure the neck below the larynx, the waist at the navel, and (for women) the hips at the widest point. Stay relaxed — don't suck in — and measure at the same time of day.
What's a healthy body fat percentage?
Rough reference bands for men: 2–5% essential, 6–13% athletic, 14–17% fitness, 18–24% average, 25%+ above average. Women carry more essential fat, so add roughly 8–10 points to each band. These are general references, not clinical thresholds.
What are fat mass and lean body mass?
Fat mass is your body weight multiplied by body-fat percentage. Lean body mass is everything else — muscle, bone, organs and water. When dieting, the aim is usually to reduce fat mass while keeping lean mass roughly constant.