Calculate body fat

Estimate body-fat percentage from the U.S. Navy circumference method and split scale weight into estimated fat and lean mass.

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ToolBody Fat Calculator
Input
Output
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Preview

How it works

The male equation combines the base-10 logarithms of abdomen minus neck circumference and height; the female equation instead uses waist plus hip minus neck. The percentage is multiplied by scale weight for fat mass, and subtracting that mass leaves the reported lean amount; no tape value is supplied automatically.

Formula
fat mass = scale weight × estimated body-fat percentage ÷ 100
  • Hip circumference is required only for the female equation because it forms part of that circumference value.
  • No athletic or health category is attached to the result because the Navy measurement protocol does not make a home estimate a diagnosis.

Worked example

Tape measurements in centimetres
A 180cm adult measuring 85cm at the waist and 38cm at the neck
Input
											Height cm: 180
Waist cm: 85
Neck cm: 38
Weight kg: 80
Sex: male
Output
												Body fat percent: 16.1
Fat mass kg: 12.88
Lean mass kg: 67.12

When to use this

Navy body-composition assessments use sex-specific circumference values and height tables; fitness logs repeat the same tape protocol over time, while home records may compare the estimate with scale weight before DXA measurement is available.

Edge cases

  • A male waist equal to or smaller than the neck is rejected before the equation can take a logarithm of zero or a negative value.
  • The female path rejects a missing hip measurement and a waist-plus-hip circumference not greater than the neck.
  • Tape position, tension, and breathing are not adjusted: the exact centimetres entered are passed into the circumference equation.

References