The metric system is easy to use because it is based on powers of 10. Because of its simplicity, the International System of Units used by scientists is based on the metric system. Some prefixes indicate larger amounts, while others indicate smaller amounts. For example, the prefix "kilo-" means 1,000 so 1 kilometer is equal to 1,000 meters. Conversely, 1 meter is equal to 0.001 kilometers.
The basic metric unit of length is the meter (m). When measuring small distances, centimeters (cm) or millimeters (mm) are often used instead. When measuring large distances, kilometers (km) are often used. These three alternative units are equal to 0.01 meters, 0.001 meters and 1,000 meters, respectively.
The standard metric unit of volume depends on the phase of matter being measured. Liters (L) are used for liquids and gases, while cubic meters (m^3) are used for solids. Milliliters (ml) are often used for quantifying small volumes. The metric system was designed so that 1 ml is equal to 1 cubic centimeter (1 cm^3).
The basic metric unit of mass is the kilogram (kg). Kilograms are the only basic unit to contain a metric prefix. For quantifying small masses, grams (g) or milligrams (mg) are used instead. Micrograms (µg) are used in microbiology and other laboratory work for extremely small masses.
The standard metric unit of temperature is the Kelvin (K). Kelvins are not normally combined with metric prefixes. To convert Kelvins to degrees Celsius, simply subtract 273 degrees. From there, the following formula can be used to convert to degrees Fahrenheit: degrees Fahrenheit = 9(degrees Celsius)/5 + 32. Unlike Celsius and Fahrenheit temperatures, temperatures expressed on the Kelvin scale are referred to in Kelvins, not degrees Kelvin.