Body Fat Calculator
Estimate your Body Fat Percentage using the official US Navy circumference method (neck, waist, hip, height).
About the Body Fat Calculator
The CalcNest Body Fat Calculator uses the US Navy circumference equations to calculate your body fat percentage and lean muscle mass. Unlike simple BMI, body fat percentage distinguishes between dense muscle tissue and adipose fat.
Mathematical Formula
Men: %BF = 495 / (1.0324 - 0.19077 × log₁₀(waist - neck) + 0.15456 × log₁₀(height)) - 450
Women: %BF = 495 / (1.29579 - 0.35004 × log₁₀(waist + hip - neck) + 0.22100 × log₁₀(height)) - 450 Official United States Navy body circumference method for estimating relative body fat percentage and lean body mass without expensive DXA scans.
Variables & Components
Worked Example: Male, 178cm, 75kg, 38cm Neck, 84cm Waist
Suppose a male athlete measures his circumferences to track lean muscle vs fat tissue.
Step-by-Step Calculation
- Calculate (Waist - Neck): 84 - 38 = 46 cm.
- Calculate log₁₀(46) = 1.6628 and log₁₀(178) = 2.2504.
- Apply US Navy formula: 495 / (1.0324 - 0.19077 × 1.6628 + 0.15456 × 2.2504) - 450.
- Result = 14.8% Body Fat (Fitness Category).
- Fat Mass = 75 × 0.148 = 11.1 kg | Lean Muscle Mass = 75 - 11.1 = 63.9 kg.
How to Use This Calculator
Select your biological sex (Male or Female).
Enter your standing Height and current Body Weight.
Measure and enter your Neck and Waist circumferences (and Hip circumference for females).
View your estimated Body Fat Percentage, ACE fitness classification, and lean mass breakdown.