Body Fat Calculator - US Navy Circumference Method

Body Fat Calculator

This calculator estimates body fat percentage with the U.S. Navy circumference method, developed by Hodgdon and Beckett for the U.S. Navy body composition program. It converts neck, waist, height, and, for women, hip measurements into a percentage, then places the result on a six-band scale from essential fat to obese. The tool applies a separate formula for men and women and accepts both metric and imperial input.

How the calculation works

The 1984 Navy study found that circumference measurements predicted body density almost as well as skinfold calipers, without needing any special equipment. Height and neck circumference act as fixed reference points, while waist, and hip for women, capture the tissue that changes with body composition. Every measurement is converted to centimeters before the formula runs, even when you enter feet, inches, or pounds.

Men:   BF% = 495 / (1.0324 - 0.19077 × log10(waist - neck) + 0.1554 × log10(height)) - 450
Women: BF% = 495 / (1.29579 - 0.35004 × log10(waist + hip - neck) + 0.2210 × log10(height)) - 450
(all measurements in centimeters)

Worked example

Take a 178 cm man with a 39 cm neck and an 80 cm waist. Waist minus neck is 41 cm, so the formula returns 495 / (1.0324 - 0.19077 × log10(41) + 0.1554 × log10(178)) - 450 = 10.7% body fat, which falls in the Athletes band below.

Body fat percentage categories

The bands below follow the American Council on Exercise (ACE) body composition classification, the reference most U.S. Navy method calculators use to label results. This is a fitness reference, not a medical diagnosis, so a doctor or registered dietitian is the right source for health guidance tied to body composition.