Body Fat Calculator
Estimate your body fat percentage using the US Navy method based on simple body measurements. No special equipment needed.
Results
Body Fat Categories (Men)
How to Use This Tool
- Select your gender (Male or Female) — the calculator uses a different formula for each.
- Enter your height in centimeters and weight in kilograms.
- Measure and enter your waist circumference (at the navel) and neck circumference (at the narrowest point) in centimeters.
- If you selected Female, also enter your hip circumference (at the widest point).
- View your estimated body fat percentage, fat mass, lean mass, and where you fall on the body fat category scale.
Formula & How It Works
Unit Conversion
inches = centimeters × 0.393701The US Navy formula's constants were derived using inch measurements, so all height, waist, neck, and hip values you enter (in cm) are first converted to inches before the formula is applied.
US Navy Formula — Men
Body Fat % = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76Waist and neck circumferences (in inches) are combined as a single difference, then compared against height (in inches) using base-10 logarithms.
US Navy Formula — Women
Body Fat % = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387For women, waist and hip circumferences are added and neck is subtracted (all in inches), then compared against height using the same logarithmic method.
Fat Mass & Lean Mass
Fat Mass = Weight × (Body Fat % ÷ 100), Lean Mass = Weight − Fat MassOnce body fat percentage is known, it is applied directly to your total body weight to split it into fat and lean (muscle, bone, water, organs) components.
Practical Examples & Common Use Cases
Example — Male, 175 cm, 75 kg
Waist 85 cm, neck 38 cm, height 175 cm convert to about 33.46 in, 14.96 in, and 68.90 in. Body Fat % = 86.010 × log10(33.46 − 14.96) − 70.041 × log10(68.90) + 36.76 ≈ 17.0%. That falls right at the edge of the "Fitness" category. At 75 kg, fat mass ≈ 12.8 kg and lean mass ≈ 62.2 kg.
Example — Male, 180 cm, 80 kg (leaner build)
Waist 80 cm, neck 40 cm, height 180 cm convert to about 31.50 in, 15.75 in, and 70.87 in. Body Fat % = 86.010 × log10(31.50 − 15.75) − 70.041 × log10(70.87) + 36.76 ≈ 10.1%. That falls in the "Athletic" category. At 80 kg, fat mass ≈ 8.1 kg and lean mass ≈ 71.9 kg.
Example — Female, 163 cm, 60 kg
Waist 70 cm, neck 31 cm, hip 95 cm, height 163 cm convert to about 27.56 in, 12.20 in, 37.40 in, and 64.16 in. Body Fat % = 163.205 × log10(27.56 + 37.40 − 12.20) − 97.684 × log10(64.16) − 78.387 ≈ 26.2%. That falls in the "Average" category. At 60 kg, fat mass ≈ 15.7 kg and lean mass ≈ 44.3 kg.
Frequently Asked Questions
The US Navy method is accurate within 3-4% of more advanced methods like DEXA scans. It is more reliable than BMI for assessing body composition, especially for muscular individuals.
Waist: at the navel level, relaxed (do not suck in). Neck: at the narrowest point below the Adam's apple. Hip (women): at the widest point of the buttocks. Measure with a flexible tape, snug but not compressing.
For men: 14-24% is average, 6-13% is athletic. For women: 25-31% is average, 14-20% is athletic. Essential fat minimums are 2-5% (men) and 10-13% (women).
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