Body Fat Calculator

Using the body fat estimate

The US Navy method estimates body-fat percentage from height and tape measurements. It does not directly measure fat tissue, and a body-category label is not a diagnosis. The tool is useful for understanding the equation and comparing consistently collected measurements over time. Small differences in where or how tightly you measure can affect the result, so apparent precision in a decimal should not be mistaken for laboratory accuracy or a definitive assessment of health.

Step-by-step inputs

1. Units. Replace the starting value with your own, keeping the displayed unit and period. Starting example: US .
2. Sex. Choose the equation used for your scenario. The male and female options use different measurement combinations; they do not describe every person's body composition accurately. Starting example: Male .
3. Height. Enter total height in inches. A height of five feet ten inches is 70 inches, not 5.10. Starting example: 70 in.
4. Waist. Measure the circumference at the location named by the field, keeping the tape level and using consistent conditions each time. Do not substitute a clothing size. Starting example: 34 in.
5. Neck. Enter the neck circumference in inches. Waist-minus-neck is part of the male equation, so incorrect or impossible measurements can invalidate the estimate. Starting example: 15 in.

Worked example with the starting values

Using the starting inputs, the estimate is Estimated body fat: 17.5% .

The equation uses logarithms of circumference combinations and height. The starting example represents the entered tape measurements, not a recommended physique. Changing one circumference demonstrates mathematical sensitivity; it is not a prediction that a particular change in body fat will alter that measurement by the same amount.

US Navy circumference estimate

Estimated lean-mass share

82.5%

Compare waist scenarios

Height, neck and equation selection remain at their starting values. These are measurement scenarios, not recommended targets or promised changes from a diet.

Make a useful comparison

Measure at the same location with similar tape tension before comparing two results. A measurement change caused by technique can look like a body-composition change. If tracking a trend is useful for you, record the measurements as well as the estimated percentage rather than only saving the final number.

Read the number alongside broader health information. Strength, nutrition, symptoms, medical history and other observations may matter more than a formula-derived category. The same estimated percentage can have different implications for different individuals.

Ask a qualified professional when an estimate is unexpected or would influence a health decision. More specialized assessment may be appropriate, but no method's output should be used alone to diagnose a condition or justify aggressive dieting.

Common mistakes to avoid

• All linear measurements here are in inches. Entering centimeters without conversion changes the equation's meaning and can produce a plausible-looking but incorrect number.
• An invalid logarithm input is not a valid zero-body-fat finding. Recheck the measurements if neck and waist combinations are impossible or the result is implausible.
• Tape-based equations have individual error and population limitations. Do not assume the calculator guarantees a particular accuracy against a laboratory method, or use its categories as treatment thresholds.