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Body composition

Body fat calculator

Body fat percentage from tape measurements using the US Navy formula.

Your stats

Measure waist at the navel; neck just below the larynx; hip (women) at the widest point. Tape should be snug, not tight.

Body fat percentage
17.5%

Category: Fitness.

The US Navy tape method is accurate to within ±3 % for most adults when measurements are taken carefully — close to DEXA, much cheaper.

The US Navy method

The US Navy developed this method to screen recruits without expensive equipment. It uses circumference measurements — neck, waist, and (for women) hip — combined with height. It is calibrated against hydrostatic weighing and tends to land within ±3 % of more expensive methods.

It is the best free option for tracking change over time. The absolute number is approximate; the direction it moves is usually accurate.

The formulas

Male:   BF % = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76
Female: BF % = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387

All measurements in inches. Metric inputs are converted automatically.

Frequently asked questions

How accurate is the US Navy method?
Within about ±3 % for most adults when measurements are taken carefully. Less reliable for very lean or very heavy individuals, and for those carrying unusual body-fat distributions. DEXA scans are more accurate but cost money; the Navy method is free and close enough for tracking change over time.
Where exactly do I measure?
Neck: just below the larynx, tape angled slightly downward at the front. Waist: at the navel for men, at the narrowest point for women. Hip (women only): at the widest point of the hips. Tape should be snug against the skin without compressing it.
Why are men and women treated differently?
Women carry more essential body fat (for hormonal and reproductive function) and store fat differently. The hip measurement helps the formula account for that distribution. Essential-fat minimums are roughly 3 % for men and 12 % for women.
Should I measure morning or evening?
Morning, before eating or drinking, after using the bathroom. Hydration and bloating affect waist measurements noticeably over the course of a day. Be consistent — same time, same tape, same body position.

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