Metric system

The metric system of measurement is a base-ten system of measurement. Units in the metric system can have prefixes added to them to indicate a multiple or submultiple (of a power of 10) of the unit. The metric system was developed in France in the late 1700s and since then, various forms of the metric system have been used throughout the world. One exception is the United States, where the US customary system of measurement is used in most everyday situations. The United Kingdom also still uses the imperial system to a degree, but has adopted the metric system and largely metricated, unlike the US.

The modern form of the metric system is called the International System of Units (SI). It shares many of the same properties of the metric system including the use of base units, derived units, and metric/SI prefixes. It is the only system of measurement that has an official status in virtually every country around the world.

Some of the units of the metric system are shown in the following table:


Base units

The metric system uses base units, which are units that are chosen as a measurement of a base quantity such as length, weight/mass, volume/capacity, and more. Below are some of the base units in older versions (not SI) of the metric system:

Base units can be modified by prefixes that indicate what multiple or submultiple of the base unit is being represented.


Group 1 prefixes

Group 1 uses the Latin prefixes milli-, centi-, and deci-. These prefixes, added to words expressing measurement, indicate that the base unit has been divided by some power of 10. Note that all the units in Group 1 are smaller than the base unit.

1 millimeter = 0.001 meters

1 centimeter = 0.01 meters

1 decimeter = 0.1 meters


1 milligram = 0.001 grams

1 centigram = 0.01 grams

1 decimeter = 0.1 grams


1 milliliter = 0.001 liters

1 centiliter = 0.01 liters

1 decileter = 0.1 liters


Group 2 prefixes

Group 2 uses the Greek prefixes deca-, hecto-, kilo-. These prefixes indicate that the base unit has been multiplied by some power of 10. Note that all the units in Group 2 are larger than the base unit.

1 decameter = 10 meters

1 hectometer = 100 meters

1 kilometer = 1,000 meters


1 decagram = 10 grams

1 hectogram = 100 grams

1 kilogram = 1,000 grams


1 decaliter = 10 liters

1 hectoliter =100 liters

1 kiloliter = 1,000 liters