About

Standard scales provide weight, but they fail to distinguish between fat tissue and lean muscle mass. This distinction is critical for athletes, bodybuilders, and anyone monitoring metabolic health. The Body Composition Calculator utilizes the US Navy Method, a widely accepted algorithm that estimates body density based on circumference measurements of the neck, waist, and hips relative to height. Unlike bioimpedance scales, which fluctuate with hydration levels, anthropometric measurements offer consistent trend data.

Understanding your Lean Body Mass (LBM) allows for precise caloric adjustments. A drop in weight accompanied by a drop in LBM suggests muscle loss, often a sign of excessive caloric deficit or insufficient protein intake. Conversely, weight gain with stable body fat percentage indicates successful muscle hypertrophy. This tool separates these variables.

Formulas

The calculator employs the US Navy Circumference Method. The equations differ by biological sex due to adipose tissue distribution patterns.

Men:

%Fat = 86.010 × log₁₀(abdomen − neck) − 70.041 × log₁₀(height) + 36.76

Women:

%Fat = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387

All measurements inside the logarithmic function must be in centimeters.

Reference Data

Classification	Women (% Fat)	Men (% Fat)	Description
Essential Fat	10-13%	2-5%	Critical physiological limit
Athletes	14-20%	6-13%	High performance, muscle definition
Fitness	21-24%	14-17%	Visibly lean, healthy range
Average	25-31%	18-24%	General population standard
Obese	≥ 32%	≥ 25%	Increased health risk

Frequently Asked Questions

Subcutaneous fat storage patterns differ by individual, but the neck is generally resistant to localized fat gain compared to the abdomen. Comparing the neck circumference to the waist (men) or hips (women) provides a reliable ratio for estimating total body density without using calipers.

Unlike bioelectrical impedance analysis (BIA), which sends a current through water in the body, this anthropometric method is unaffected by hydration. This makes it superior for tracking progress over short durations where water weight fluctuations might skew scale readings.

BMI (Body Mass Index) is a simple ratio of weight to height and cannot distinguish between muscle and fat. A bodybuilder may have an "Obese" BMI but a low body fat percentage. This calculator solves that error by isolating adipose tissue from lean mass.

Take measurements in the morning, fasting, after using the restroom. This minimizes bloating (waist expansion) from food intake, ensuring consistency in the data points.