Body Fat Percentage Calculator
Estimate your body fat percentage using the U.S. Navy circumference method based on waist, neck, and height measurements.
Results
Visualization
How It Works
The U.S. Navy body fat formula estimates body fat percentage from simple circumference measurements. It was developed to provide a quick field assessment without specialized equipment like DEXA scans or calipers, and is widely used by military and fitness professionals.
The Formula
Variables
- waist — Circumference at the navel (cm)
- neck — Circumference just below the larynx (cm)
- height — Standing height in centimeters
- hip — Hip circumference, used in the female formula (cm)
- %BF — Estimated body fat percentage
- weight — Total body weight used to derive fat and lean mass (kg)
Worked Example
A 70 kg male with a 80 cm waist, 38 cm neck, and 170 cm height: log10(80-38) = log10(42) = 1.623, log10(170) = 2.230. %BF = 495 / (1.0324 - 0.19077*1.623 + 0.15456*2.230) - 450 = approximately 17.7%. Fat mass = 70 * 0.177 = 12.4 kg, lean mass = 57.6 kg.
Practical Tips
- Measure your waist at navel level, standing relaxed, without sucking in your stomach.
- Take neck measurements just below the Adam's apple with the tape slightly sloping downward at the front.
- Measure at the same time of day for consistency, ideally in the morning before eating.
- The Navy method has a margin of error of about 3-4%, so treat results as estimates.
- For women, hip circumference is also needed for the most accurate Navy formula result.
Frequently Asked Questions
How accurate is the Navy body fat method?
Studies show the Navy method is accurate to within about 3-4% of DEXA scan results for most people. It tends to be less accurate at very low or very high body fat levels. For a free, equipment-free estimate, it is one of the best options available.
What is a healthy body fat percentage?
For men, 10-20% is generally considered healthy, with athletes often in the 6-13% range. For women, 18-28% is healthy, with athletes at 14-20%. Essential fat minimums are about 3% for men and 12% for women.
Why does the formula use waist and neck?
Waist circumference correlates strongly with abdominal fat, while neck circumference acts as a proxy for frame size. The difference between them helps isolate the fat component from skeletal structure.
Can I use this calculator if I am very muscular?
Muscular individuals may get slightly overestimated body fat readings because a larger waist (from oblique muscles) inflates the calculation. Hydrostatic weighing or DEXA scans are more accurate for highly muscular people.
How often should I measure body fat?
Every 4-6 weeks is ideal when tracking progress. Body fat changes slowly, so daily measurements will mostly reflect hydration and measurement variability rather than real changes.