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Body Fat Percentage Calculator (Navy Method)

Estimate body fat percentage from neck, waist, and hip measurements using the US Navy circumference formula.

Estimated body fat
19.4%

What this calculates

Body fat percentage tells you what fraction of your body weight is fat versus everything else (muscle, bone, organs, water). It's more useful than BMI for assessing fitness because two people with the same BMI can have very different body compositions. The US Navy circumference method uses neck, waist, and (for women) hip measurements and is reasonably accurate without specialized equipment.

Formula & how it works

Men: %BF = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76. Women: %BF = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387. All measurements in inches. Convert from cm by dividing by 2.54. Categories (men): essential 2–5 %, athlete 6–13 %, fit 14–17 %, average 18–24 %, obese 25 %+. Women: essential 10–13 %, athlete 14–20 %, fit 21–24 %, average 25–31 %, obese 32 %+.

Worked example

Man, 70 in tall, 36 in waist, 16 in neck. %BF = 86.010 × log10(36 − 16) − 70.041 × log10(70) + 36.76 = 86.010 × 1.301 − 70.041 × 1.845 + 36.76 ≈ 112 − 129 + 36.76 ≈ 19.8 %. That's the high end of 'average' — getting toward needing a recomp.

Frequently asked questions

How accurate is the Navy method?

Within ±3 % for most people compared to DEXA scan (the gold standard). Less accurate for very lean or very heavy people, and for those with unusual proportions. Skinfold calipers (correctly used) and BIA scales are similar ballpark.

How do I measure correctly?

Neck: just below the larynx, looking straight ahead. Waist: at the narrowest point for women, at the navel for men. Hip (women): widest point around the buttocks. Measure relaxed, not flexed or sucked-in. Take 3 measurements and average.

What's a healthy body fat percentage?

Men: 10–20 % is the broadly healthy range; under 10 % is athletic/show-condition. Women: 18–28 %; under 18 % may affect menstrual cycle. Essential fat is needed for organ function — going below it is dangerous.

Should I aim for 'low' body fat?

Not necessarily. Health markers (insulin sensitivity, cardiovascular fitness, strength) matter more than a single number. Many strong, healthy people sit in the 'average' range and are fine.

Disclaimer: Estimate only. DEXA or hydrostatic weighing are more accurate if precision matters.

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