Body Fat Estimate (US Navy formula) Calculator View Calculator This Body Fat Navy Calculator uses the U.S. Navy fitness formula to get an estimated measuring of body fat percent. Use a tape measure then enter your waist, hip, and neck measurements. Combine these measurements with your gender and height and this navy calculator will estimate body fat percent, lean mass, fat mass, and your general navy fitness category. (You can see the Navy Body Fat Chart by clicking the down arrow icon right under the results.) The water displacement test is the most accurate way to determine body fat percent, but the Navy Body Fat test or YMCA formula is accurate within 1-3% for most people. Learn more about putting this calculator or other calculators on your website.