Body Fat Calculator

This uses the U.S. Navy circumference method. Measure height, neck and waist (and hip for the female equation) in one unit system.

How it works

The Navy / DoD tape test estimates percent fat from logarithms of circumferences, not from a scale.

Measurements are converted to inches, then: men 86.010 log₁₀(waist − neck) − 70.041 log₁₀(height) + 36.76; women 163.205 log₁₀(waist + hip − neck) − 97.684 log₁₀(height) − 78.387 (Hodgdon & Beckett).

Waist must exceed neck (men), and waist + hip must exceed neck (women). It is a field estimate, not imaging.

Formula

Male: 86.010 log₁₀(waist − neck) − 70.041 log₁₀(height) + 36.76
Female: 163.205 log₁₀(waist + hip − neck) − 97.684 log₁₀(height) − 78.387
(all lengths in inches)

Worked examples

Male tape example
70 in height, 16 in neck, 34 in waist → about 15.4%

Useful notes

Same family of equations as the Army tape test; that page labels the AR 600-9 context.
Not medical advice.

FAQ

Where do I measure waist?: The Navy male equation uses the abdomen at the navel. Follow a consistent tape path; the equation cannot correct a bad measurement.
Is this as accurate as DEXA?: No. It is a circumference estimate with known error, used because a tape is cheap.
Why was my result rejected?: The log arguments must be positive. Waist has to be larger than neck (and hip is required for the female equation).

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