How to use this calculator
- Enter or choose sex.
- Enter or choose units.
- Enter or choose height.
- Enter or choose neck.
- Enter or choose waist.
- The body fat updates as you type. Use Copy result or Share to keep it.
Method
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 in inches)
- waist, neck, hip
- circumferences in inches (cm ÷ 2.54)
- height
- standing height in inches
Worked example
- Convert to inches: height 178 ÷ 2.54 = 70.08, neck 14.96, waist 33.86; waist − neck = 18.90.
- 86.010 × log10(18.90) = 86.010 × 1.2765 = 109.79.
- 70.041 × log10(70.08) = 70.041 × 1.8456 = 129.27.
- %BF = 109.79 − 129.27 + 36.76 = 17.3%. Fat mass = 80 × 0.173 ≈ 13.8 kg; lean mass ≈ 66.2 kg.
A man 178 cm tall with a 38 cm neck and 86 cm waist has an estimated 17.3% body fat: about 13.8 kg of fat and 66.2 kg of lean mass at 80 kg.
What the result means
Use the result to follow a trend: measure the same way, at the same time of day, every few weeks. A change of a percentage point or two between single measurements is within the method’s error. Waist size on its own is also a useful health marker.
Assumptions and limits
- US Navy circumference equations (Hodgdon and Beckett, Naval Health Research Center, 1984), developed on adult military personnel.
- Measurements taken with a non-stretch tape, snug but not compressing the skin.
- For an individual, results can differ from laboratory methods (such as DXA) by several percentage points.
- Less reliable for very lean, very muscular or very large bodies, older adults and pregnancy.
- Not a diagnosis; there is no single agreed set of healthy body-fat cut-offs, so none is shown.
Questions
Is this the same as the Army tape test?
The Navy two- and three-site equations were used by several US services, but the US Army replaced its tape test with a waist-to-height ratio in July 2026. See the Army Body Composition Calculator for the current Army check.
Why do women need a hip measurement?
Women carry more fat around the hips and thighs, so the female equation adds the hip circumference to improve the estimate.
Sources
Please note: This is a general screening estimate for adults, not medical advice or a diagnosis. Talk to a qualified health professional about your health.