Metre Convention

The Metre Convention (French: Convention du Mètre), also known as the Treaty of the Metre,^[1] is an international treaty that was signed in Paris on 20 May 1875 by representatives of 17 nations: Argentina, Austria-Hungary, Belgium, Brazil, Denmark, France, Germany, Italy, Peru, Portugal, Russia, Spain, Sweden and Norway, Switzerland, Ottoman Empire, United States of America, and Venezuela.

The treaty created the International Bureau of Weights and Measures (BIPM), an intergovernmental organization, under the authority of the General Conference on Weights and Measures (CGPM) and the supervision of the International Committee for Weights and Measures (CIPM). These organizations coordinate international metrology and the development of internationally recognized systems of measurement.

The Metre Convention established a permanent organizational structure for member governments to act in common accord on all matters relating to units of measurement. The governing organs of the BIPM are:

• The General Conference on Weights and Measures (Conférence générale des poids et mesures or CGPM)—the plenary organ of the BIPM which consists of the delegates of all the contracting governments, and
• The International Committee for Weights and Measures (Comité international des poids et mesures or CIPM)—the direction and supervision organ composed of 18 prominent metrologists from 18 different member states

The headquarters or secretariat of the BIPM is at Saint-Cloud, France. It employs around 70 people and hosts BIPM's formal meetings.

Initially the scope of the Metre Convention covered only units of mass and length. In 1921, at the sixth meeting of the CGPM, convention was amended to its scope to other fields in physics. In 1960, at the eleventh meeting of the CGPM, its system of units was named the International System of Units (Système international d'unités, abreviateed SI).^[2]

The Metre Convention provides that only nations can be members of the BIPM. In 1999, the CGPM created in the status of associate, to allow non-member states and economic entities to participate in some activities of the BIPM through their national metrology institutes (NMIs).

As of 13 January 2020^[update], the CGPM had 62 members and 40 associates.

Membership in the CGPM requires payment of substantial fees. Being in arrears with these payments over a span of years has led to expulsion of some former members.