Meter

A meter (m), or metre, is the base unit of length in the International System of Units (SI), which is the modern form of the metric system. SI is the only system of measurement that is officially accepted in most countries around the world.

In the US, SI is used in many contexts, but for everyday use, the US still uses many units within the US customary system of units. Below are some relationships between meters and other common measurements of length in both SI and the US customary system of units:

SI prefixes and the meter

In SI, each base unit can have a prefix that indicates that the value is a factor of the base unit. A few common examples include centimeters, millimeters, and kilometers. A centimeter is meters, a millimeter is meters, and a kilometer is 1000 meters.

This means that as long as we know what factor of the base unit is indicated by a given SI prefix, we can convert between values with different prefixes by simply multiplying or dividing by a power of 10.