::Metric system


Units::system    Title::metric    Center::align    First::measure    Second::metre    Units::french

{{ safesubst:#invoke:Unsubst||$N=Use dmy dates |date=__DATE__ |$B= }} Unknown extension tag "indicator"{{#invoke:Category handler|main}} {{#invoke:Hatnote|hatnote}}

  Countries which have officially adopted the metric system
  Countries which have not officially adopted the metric system (United States, Burma and Liberia)
"The metric system is for all people for all time." (Condorcet, 1791). Four everyday measuring devices that have metric calibrations: a tape measure calibrated in centimetres, a thermometer calibrated in degrees Celsius, a kilogram weight, and an electrical multimeter that measures volts, amperes and ohms.

The metric system is an internationally agreed decimal system of measurement. It was originally based on the mètre des Archives{{#invoke:Category handler|main}} and the kilogramme des Archives{{#invoke:Category handler|main}} introduced by the First French Republic in 1799, but over the years the definitions of the metre and the kilogram have been refined, and the metric system has been extended to incorporate many more units. Although a number of variants of the metric system emerged in the late 19th and early 20th centuries, the term is now often used as a synonym for "SI"<ref name=French group=Note>The following abbreviations are taken from the French rather than the English texts:

The metric system has been officially sanctioned for use in the United States since 1866, but the US remains the only industrialised country that has not adopted the metric system as its official system of measurement. Many sources also cite Liberia and Burma as the only other countries not to have done so. Although the United Kingdom uses the metric system for most official purposes, the use of the imperial system of measure, particularly among the public, is widespread and is permitted by the law.

Although the originators intended to devise a system that was equally accessible to all, it proved necessary to use prototype units in the custody of national or local authorities as standards. Control of the prototype units of measure was maintained by the French government until 1875, when it passed to an inter-governmental organisation—the General Conference on Weights and Measures (CGPM).<ref name=French group=Note />

From its beginning, the main features of the metric system were the standard set of inter-related base units and a standard set of prefixes in powers of ten. These base units are used to derive larger and smaller units that could replace a huge number of other units of measure in existence. Although the system was first developed for commercial use, the development of coherent units of measure made it particularly suitable for science and engineering.

The uncoordinated use of the metric system by different scientific and engineering disciplines, particularly in the late 19th century, resulted in different choices of base units, even though all were based on the same definitions of the metre and the kilogram. During the 20th century, efforts were made to rationalise these units, and in 1960 the CGPM published the International System of Units, which has since then been the internationally recognised standard metric system.

Metric system sections
Intro   Features    History    Variants    Relating SI to the real world    Usage around the world    Conversion between SI and legacy units    Future developments    See also    Notes    References    External links   

PREVIOUS: IntroNEXT: Features