Body Fat Calculator
Estimate adult body-fat percentage from height and circumference measurements using historical U.S. Navy equations. The required tape measurements depend on the equation selected.
Calculator arithmetic runs locally in your browser and does not require an API.
The interactive calculator loads here when JavaScript is enabled.
How to use Body Fat Calculator
Measure neck below the larynx. The male equation uses abdomen at the navel; the female equation uses the narrowest waist and widest hip circumference. Keep tape placement and tension consistent. After changing units, re-enter all measurements in the new units.
Formula and method
With lengths in inches: male % = 86.010 log10(abdomen − neck) − 70.041 log10(height) + 36.76. Female % = 163.205 log10(waist + hip − neck) − 97.684 log10(height) − 78.387. Metric inputs are converted to inches first.
Understanding the results
Tape location, posture and measurement variation affect the estimate. The model is not a clinical assessment or a military eligibility test. Nonpositive circumference differences and results outside 0%–100% are rejected rather than presented as valid estimates.
Worked example
Using the male equation with height 70 in, neck 15 in and abdomen 36 in gives an estimated 21.25% body fat. These correspond to 177.8 cm, 38.1 cm and 91.44 cm.
Results are estimates for general information, not a diagnosis or a substitute for professional medical advice.
References
Frequently asked questions
Why does the female equation need hip circumference?
It uses waist plus hip minus neck, whereas the male equation uses abdomen minus neck.
Why might another assessment give a different percentage?
Different methods estimate body composition differently, and tape measurements introduce variation.
Is the result a diagnostic category?
No. This page reports the equation estimate without a diagnostic or military pass/fail classification.