Body Fat Calculator
Calculate body fat percentage, lean mass, and BMI using the U.S. Navy method with simple tape measurements.
Measurements
All measurements should be taken in a relaxed standing posture.
Body Composition Summary
Body fat percentage
18.8%
Body fat mass
15.4 kg (34.0 lb)
Lean body mass
66.6 kg (146.8 lb)
BMI
25.9 kg/m²
BMI is provided for context; it does not measure body fat distribution.
Classification
Average range
Height
1.78 m • 70.1 in
Neck
40.0 cm • 15.7 in
Waist
90.0 cm • 35.4 in
How to Use This Calculator
Take accurate tape measurements
Measure the neck just below the larynx with slight head elevation. Measure the waist horizontally at the navel (men) or narrowest waist (women). Women also measure hips at the widest point of the buttocks.
Enter body weight and height
Use a reliable scale and stadiometer. Switch units if you prefer imperial measurements—we convert everything automatically.
Review fat mass and lean mass
Use the body fat percentage, fat mass, and lean mass to guide nutrition, training, or medical decisions. Track over time to monitor progress.
Formula
Male: Body Fat % = 86.010 × log10(Waist − Neck) − 70.041 × log10(Height) + 36.76
Female: Body Fat % = 163.205 × log10(Waist + Hip − Neck) − 97.684 × log10(Height) − 78.387
- All measurements are in inches for the formula. Centimeter inputs are converted automatically.
- Waist is measured at the level of the navel for men and the narrowest waist for women.
- Hip measurement is required for women.
- The equations are derived from the U.S. Navy Physical Readiness Test standards.
Example (Male): Height = 70 in, Neck = 16 in, Waist = 34 in → Body Fat % ≈ 15.3%.
Understanding the Results
Body fat percentage quantifies how much of your body mass is composed of adipose tissue. Tracking body fat helps evaluate nutrition plans, athletic conditioning, and health risks more accurately than weight alone. Lean body mass reflects muscle, bone, organs, and fluids.
The U.S. Navy method provides a practical estimate, but it can be sensitive to measurement technique. For the most accurate monitoring, measure at the same time of day, in similar clothing, and after exhaling normally. Pair the results with professional assessments when making major health decisions.
Frequently Asked Questions
How does this compare to caliper measurements?
Skinfold calipers sample subcutaneous fat at specific sites. The Navy method uses circumferences that capture both subcutaneous and visceral fat. Both are estimates—choose the method you can repeat consistently.
Can hydration or bloating affect measurements?
Yes. Abdominal bloating or fluid retention can increase waist circumference and temporarily raise body fat estimates. For trend tracking, measure under similar conditions.
What if my body fat result is negative or unrealistic?
Unrealistic values typically mean the tape measurements were entered incorrectly. Re-measure and ensure waist > neck (and waist + hip > neck for women).
Is this method suitable during pregnancy?
No. Pregnancy significantly alters waist and hip measurements. Use pregnancy-specific guidance from your healthcare provider instead.