Knowing your weight is just one small part of understanding your health. This Perfect Fitness Body Fat Scale uses a method of Bioelectrical Impedance Analysis (BIA) to estimate your body fat and total body water. It does this by sending a harmless amount of electricity into your body. Then, it estimates from the measured impedance of your body the percentage total body water and percentage total body fat. The scale is also equipped with an Athlete mode for people with a more athletic build. The calorie predictor function estimates the number of calories required based on your body composition and the personal data you enter.