Calculates body fat and hydration %. Displays weight and change in weight for up to 4 users. One-button SAVE function stores up to 19 entries per user. Accurately measures weight up to 375 lbs in 0.2 lb increments. FDA approved BIA (bioelectrical impedance analysis) measures body fat by passing tiny electrical impulses through the body. The electrical current reacts to fat & muscle by measuring resistance to the current. more info