Fig. 3—The standard meter.
The standard unit of volume or capacity is the liter. It is a cube one-tenth of a meter on each edge. It is equal to 1.057 quarts. It corresponds, therefore, to the quart in English measure.
Fig. 4.—Centimeter and inch scales.
The standard unit of mass is the kilogram. It is the mass of 1 liter of pure water at the temperature of its greatest density, 4°C. or 39.2°F.
The three principal units of the metric system, the meter, the liter, and the kilogram, are related to one another in a simple manner, since the liter is a cube one-tenth of a meter in each dimension and the kilogram is the mass of a liter of water. (See Fig. 5.)
The metric system is a decimal system that is, one unit is related to another unit in the ratio of ten or of some power of ten. This is indicated by the following tables:
| Metric Table of Length | |
| 10 millimeters (mm.) | equal 1 centimeter. |
| 10 centimeters (cm.) | equal 1 decimeter. |
| 10 decimeters (dm.) | equal 1 meter. |
| 10 meters (m.) | equal 1 dekameter. |
| 10 dekameters (Dm.) | equal 1 hectometer. |
| 10 hectometers (hm.) | equal 1 kilometer. |
| 10 kilometers (km.) | equal 1 myriameter. |
The measures commonly used are the centimeter, meter and kilometer.