
Many different units of length have been used across the world. The main units in modern use are U.S. customary units in the United States and the Metric system elsewhere. British Imperial units are still used for some purposes in the United Kingdom and some other countries. The metric system is subdivided into SI and nonSI units.
Common units of length in the International System of Units (SI) are:
NonSI units of length include:
Common Imperial units and U.S. customary units of length include:
In addition, the following are used by mariners:
Surveyors in the United States continue to use:
Astronomical measure uses:
Archaic units of distance include:
In everyday conversation, and in informal literature, it is common to see lengths measured in units of objects of which everyone knows the approximate width. Common examples are:
Horse racing keeps alive:
Physics also uses:


A unit of length is a way of measuring length or distance.
Common units of length in the International System of Units (SI) are:
But there are a lot of units that do not fit in the SISystem:
Common Imperial units and U.S. customary units of length include:
In addition, the following are used by mariners:
Surveyors in the United States continue to use:
Horse racing keeps alive:
Astronomical measure uses:
Physics also uses:
Old units of distance are:
In everyday conversation, and in informal literature, it is common to see lengths measured in units of objects of which everyone knows the approximate width. Common examples are:
