How much Body Fat are you carrying? Find out if you are in the healthy range. This Body Fat calculator is based on a formula developed by the US Navy.First, your body fat percentage is simply the percentage of fat your body contains. If you weigh 140 pounds and are 10% fat, it means that your body consists of 14 pounds fat and 126 pounds lean body mass (bone, muscle, organ tissue, blood,...).A certain amount of fat is essential to bodily functions. Fat regulates body temperature, cushions and insulates organs and tissues and is the main form of the body's energy storage.