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Circumference Method

Army Body Fat Calculator — Circumference Method

Estimate body fat percentage using the US Army's circumference-based method — a tape-measure formula that only needs your height, neck, and waist (plus hips for women).

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📏 Enter Your Measurements

♂ Male
♀ Female
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

📊 Estimated Body Fat

Enter your measurements and calculate
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Disclaimer: This calculator provides a general educational and fitness-tracking estimate only, not medical advice or an official military fitness assessment. Measurement technique significantly affects accuracy — consult a doctor, registered dietitian, or fitness professional for a personal body composition assessment, especially before making health or training decisions based on the result.

How the Army Circumference Method Works

The US Army's circumference-based body fat formula is a well-established, publicly documented method that estimates body fat percentage from a handful of tape-measure readings instead of specialized equipment. It uses base-10 logarithms of the circumference differences to model how body fat scales with these measurements, calibrated separately for men and women since the two sexes distribute fat differently.

Men's Formula

%BF = 86.010 × log₁₀(Waist − Neck) − 70.041 × log₁₀(Height) + 36.76

Women's Formula

%BF = 163.205 × log₁₀(Waist + Hip − Neck) − 97.684 × log₁₀(Height) − 78.387

All measurements are in inches. Because the formula involves a logarithm of a circumference difference, the value inside the log must stay positive — for men, waist must exceed neck; for women, waist plus hip must exceed neck. If it doesn't, the formula has no valid mathematical result and the calculator will flag it rather than show a misleading number.

Worked Example

A male, height 70 inches, neck 15 inches, waist 34 inches:

Frequently Asked Questions

It's a reasonable field estimate — good enough that a branch of the military has used a version of it for decades — but it's less precise than lab methods like DEXA scans or hydrostatic weighing, which directly measure body composition. Measurement technique matters a lot here: a tape pulled too tight or too loose, or measured at the wrong landmark, can shift the result by several percentage points.
Measure your neck just below the larynx (Adam's apple), with the tape sloping slightly downward toward the front. Measure your waist at the point of minimal circumference — for most people that's roughly level with the navel — without pulling the tape tight enough to compress the skin. Women additionally measure hips at the widest point around the buttocks. Take each measurement two or three times and average them for consistency.
Men and women naturally carry and distribute body fat differently — women typically carry more essential fat and store more of it around the hips, which is why the formula for women incorporates a hip measurement that the male formula doesn't use. The two formulas were derived separately from measurement data collected on each sex, rather than being one formula adjusted after the fact.
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