About

Body Fat Percentage (BFP) is a superior metric to BMI for assessing health, as it distinguishes between lean mass and adipose tissue. Two individuals with the same weight can have vastly different health profiles depending on their body composition.

This tool utilizes the US Navy Circumference Method, widely regarded as the most accurate non-clinical estimation method. It relies on the logarithmic relationship between torso circumference (waist/hips) and height, subtracted by neck circumference (a proxy for lean muscle frame). Accuracy depends on precise tape placement: the neck measurement should be below the larynx, and the waist at the navel.

Formulas

The US Navy formula uses logarithms (log₁₀) of measurements in centimeters.

Men: %BF = 4951.0324 − 0.19077 log₁₀(W − N) + 0.15456 log₁₀(H) − 450

Women: %BF = 4951.29579 − 0.35004 log₁₀(W + Hip − N) + 0.22100 log₁₀(H) − 450

Where W=Waist, N=Neck, H=Height.

Reference Data

Category	Women Range	Men Range
Essential Fat	10 - 13%	2 - 5%
Athletes	14 - 20%	6 - 13%
Fitness	21 - 24%	14 - 17%
Average	25 - 31%	18 - 24%
Obese	32+%	25+%

Frequently Asked Questions

For the Navy Method, men should measure at the navel level. Women should measure at the narrowest point of the waist, above the navel but below the rib cage.

The Navy Method typically has a margin of error of 3-4%. While DEXA is the gold standard, this method is significantly more accurate than BMI and consistent enough to track progress over time.

A thicker neck often correlates with a larger skeletal frame or higher muscle mass. Subtracting the neck circumference helps the formula distinguish between "big boned/muscular" individuals and those carrying excess fat.