**One kilometer equals 1,000 meters.** In the International System of Units, physical quantities are represented by specific SI units. A prefix is added to represent larger and smaller multiples of each unit. The prefix "kilo" means 1,000.

The metric system, also called the International System of Units, is the world standard for measurement. It is used by scientists, and adopted by most nations as the standard. The meter, the standard unit of length, equals 39.37 inches. Other common prefixes used with the meter include "deci," or one-tenth, "centi," or one-hundredth, "milli," or one-thousandth, "micro," or one-millionth and "nano," or one-billionth. These prefixes are also attached to gram and liter to measure mass and volume, respectively.