SI units are organized in a very logical manner. For this reason, it is superior to United States customary units. All of the units are decimalized. For example, 1/100 of a meter is a centimeter, and 1000 meters is a kilometer (That's just over 0.6 of a mile). The units also "fit together". For example, one gram is the weight of one cubic centimeter of water. Temperature units are also logical. On the Celsius scale, 0° is the exact temperature at which water freezes at standard pressure. 100°C is the exact temperature at which water boils at standard pressure.