The inch is a commonly used length unit in the United States and many other countries. An inch is equal to 0.00039 meters. The inch was originally a Roman unit of length, equal to 1/12 of a foot. It became an SI unit in the early 19th century, and is now one of the six standard lengths interdependent with meters (along with meter, kilometer, millimeter, micro meter, and nano meter). In 1935, theUSEb added the “point” to the name of the inch; thus 0.0003936 meters becomes 3.62 points, or 1/32nd of an inch.

The yard is the traditional length unit of linear measure. It is traditionally equivalent to 0.9144 meters, though it has been varied between 9 and 12 feet in recent times. The yard was first conceptualized by fifth-century BC Egyptians and was standardized as 9 feet in 1795 by the French military engineer General Hoche. During the American Revolutionary War, the Continental Army was unimpressed with various proposals for a new foot measuring system and instead adopted the British yard as their standard. The use of the yard spread rapidly throughout the world after that due to its international compatibility. Today, most countries use either the metric system or a variant of it, and there are few remaining areas where yards are used; Africa mostly uses meters, India uses centimeters, parts of Asia use traditional units like li and fen.