1,500 milliliters is equal to 1.5 liters. In the metric system, a liter is the basic unit of volume for liquids. Like the rest of the metric system, the naming system uses prefixes derived from Latin and Greek roots that tell the user what fraction or multiplier the unit uses. In this example, "milia" is "thousand" in Latin. Thus, a "milli-liter" is a thousandth of a liter. Learning these prefixes makes the use of the metric system much easier.