United States customary units are a
system of measurements commonly used in the
United States. Many U.S. units are virtually identical to their
imperial counterparts, but the U.S. customary system developed from
English units used in the
British Empire before the system of
imperial units was standardized in 1824. Several
quantitative differences from the imperial system are present.
The vast majority of U.S. customary units have been defined in terms of the
meter and the
kilogram since the
Mendenhall Order of 1893 (and, in practice, for many years before that date). These definitions were refined by the international yard and pound agreement of 1959. The U.S. primarily uses customary units in its commercial activities, while science, medicine, government, and many sectors of industry use metric units.