Body Fat Calculator — U.S. Navy method
Estimate your body-fat percentage with the U.S. Navy tape method from a few measurements — in your browser.
🔒 Runs entirely in your browser. Your input and output are never sent to a server or stored — fully private.
Estimate body-fat percentage from a few tape measurements using the U.S. Navy method.
U.S. Navy circumference method. Measure relaxed, with the tape snug but not compressing the skin.
Estimates only — not medical advice.
About this tool
The U.S. Navy tape method behind this calculator needs only a tape measure and a few girth measurements, not calipers or a scan. Enter your height, neck and waist (plus hips for women) and it returns an approximate body-fat percentage and a fitness category, from essential fat to obese. It is a low-tech way to track changes over time without special equipment. Every measurement is processed in your browser, so nothing you enter is uploaded or saved.
Frequently asked questions
How do I take the measurements?
Use a flexible tape and keep it snug but not tight. Measure your neck just below the larynx, and your waist at the navel for men or at the narrowest point for women; women also measure the hips at the widest part. Stand relaxed, breathe normally, and take each reading without sucking in. Small errors in tape position change the result, so measure twice.
How accurate is the Navy method?
For most people it lands within about 3 to 4 percentage points of a clinical measurement like DEXA, which is good for a no-equipment method. It can be off for very lean, very muscular or very heavy bodies, because it assumes an average shape. Treat the trend over weeks as more meaningful than any single reading on its own.
Should I rely on this number for health decisions?
Treat it as an informational estimate, not a medical assessment. Body-fat percentage is only one signal of health, and the tape method is an approximation, so do not make drastic changes based on it alone — a doctor or qualified trainer can give proper guidance. The calculation runs locally in your browser, and the measurements you enter are never uploaded or stored.