While body fat percentage is a crucial metric, understanding your absolute fat mass and lean body mass gives you a clearer picture of your body composition. This calculator helps you break down your total body weight into two key components: fat mass (the weight of all fat in your body) and lean body mass (the weight of your muscles, bones, organs, and water). Tracking these two figures separately is more effective than just tracking weight, as it allows you to see if you are losing fat while preserving or gaining valuable muscle mass.