Body Fat Calculator
Estimate body fat percentage using the U.S. Navy circumference method.
About the Body Fat Calculator
Body fat percentage gives a more direct picture of body composition than weight or BMI alone, distinguishing lean mass from fat mass. This calculator uses the U.S. Navy circumference method, a tape-measure-based formula that is widely used because it requires no special equipment.
How It Works
The Navy method uses the logarithm of waist and neck circumference (plus hip circumference for women) relative to height to estimate body fat percentage — a statistically derived formula validated against more expensive body composition measurement methods.
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.
Example
Scenario: A man with a 175 cm height, 85 cm waist, and 38 cm neck.
Result: An estimated body fat percentage based on the Navy circumference formula.
Assumptions & Limitations
- All measurements should be taken snugly with a flexible tape measure at the specific anatomical points the Navy method specifies (waist at the navel, neck just below the larynx).
- The formula was validated primarily on adult populations and may be less accurate for very lean athletes or unusual body shapes.
- Circumference-based methods are estimates — DEXA scans, hydrostatic weighing, or bioelectrical impedance devices provide more precise body fat readings.
- Measurement technique significantly affects accuracy; inconsistent tape placement is the most common source of error.