Body Fat Calculator: Navy Method & CUN-BAE | Free

How does this calculator work?

This calculator estimates your body fat percentage using two validated methods: the US Navy circumference method and CUN-BAE. Both provide an ACE classification and break down fat mass vs. lean mass.

US Navy method

Developed by Hodgdon and Beckett (1984) for the US Department of Defense. It requires tape measurements of neck and waist circumference for men, plus hip circumference for women. The formula uses logarithmic relationships between circumferences and height to estimate body density and fat percentage, with an accuracy of ±3–4 % vs. hydrostatic weighing.

CUN-BAE method

The Clínica Universidad de Navarra–Body Adiposity Estimator (Gómez-Ambrosí et al., 2012) uses your BMI, age and sex to estimate body fat without tape measurements. Validated in 6,510 subjects against air-displacement plethysmography with r=0.89. Ideal when circumference data is not available.

ACE body fat classification

The American Council on Exercise (ACE) provides these reference ranges:

Body fat vs BMI

A 2024 JAMA study found that body fat percentage predicts all-cause mortality 1.78× more accurately than BMI alone. Unlike BMI, body fat percentage differentiates between muscle and adipose tissue, making it more clinically relevant for individuals who are muscular or have atypical body compositions.

How to measure correctly

• Neck: measure just below the larynx (Adam’s apple), tape sloping slightly downward at the front. Keep the tape snug but not compressing the skin.
• Waist: measure at the narrowest point of the torso (usually at the navel level for men). Stand relaxed, exhale normally, and keep the tape horizontal.
• Hip (women only): measure at the widest point of the buttocks. Keep feet together and the tape horizontal all around.