Body Fat Calculator
Estimate your body fat percentage in seconds with just a tape measure and the trusted US Navy method.
📖 How it works & FAQEnter your measurements to see results. This is an estimate, not medical advice.
What the US Navy body fat method is
This calculator uses the US Navy circumference (or "tape") method, a formula developed by the Naval Health Research Center to estimate body fat percentage from a few simple measurements instead of expensive equipment. All you need is a flexible tape measure. For men it uses height, neck, and waist. For women it adds a hip measurement, because fat distribution differs between sexes. The math runs on log base 10 of your measurements in inches, and it is the same approach the Navy uses for its own fitness screenings.
How accurate is it?
The tape method typically lands within about 3-4 percentage points of a DEXA scan for most people, which is impressive for a free tool. It works best for people of average build and can drift for very lean athletes or those carrying weight in unusual places. Because it relies on circumference, careful, consistent measuring matters more than anything — measure at the same spots each time and keep the tape snug but not tight. These results are estimates, not medical advice.
How to use it
- Pick your sex and preferred units (inches/pounds or centimeters/kilograms).
- Measure your neck just below the larynx, sloping slightly down to the front.
- Measure your waist at the navel for men, at the narrowest point for women.
- Women: also measure the hip at its widest point.
- Enter your height, and optionally your weight to see estimated fat mass and lean mass. Results update instantly.
FAQ
- Why does the female formula need a hip measurement?
- Women naturally store more fat around the hips, so the Navy formula includes hip circumference to improve accuracy. The male formula only uses waist and neck.
- Should I measure before or after eating?
- Measure first thing in the morning, before eating or drinking, for the most consistent readings. A full stomach can add an inch or two at the waist.
- What is a healthy body fat percentage?
- General fitness ranges are roughly 14-17% for men and 21-24% for women, but "healthy" varies by age, genetics, and goals. Talk to a professional for personalized targets.
- Is my data saved anywhere?
- No. Everything runs in your browser and nothing is uploaded, stored, or shared. Refresh the page and it is gone.