Most standard rulers are 30 centimeters long, which makes 1 centimeter equal to one-thirtieth of the length of a standard 12-inch, or 30-centimeter, ruler. The centimeter is a metric unit of measure that, according to Metric-Conversions, is equal to 0.3937 inches.
The centimeter is a standard unit of measure of length in the metric system, and it is equal to one one-hundredth of a meter. If a meter stick is divided into 100 equal pieces, each one of the pieces is measured as 1 centimeter in length. Inches are a comparable unit of measure of length in the English system. A single inch is equivalent to 2.54 centimeters, so length in inches can be converted to centimeters by multiplying the inches measured by 2.54.
According to Dictionary.com, the word "centimeter" has been in use since the 1800s. It comes from the French word "centum," which means "hundred," and the root of the word is "meter." The standard abbreviation for the word "centimeter" is "cm." Most rulers also show each centimeter sub-divided into 10 smaller, equal portions. These indicate the length of 1 millimeter, which is equal to one one-thousandth of a meter. There are 25.4 millimeters in a single inch.