Metre Convention

The Metre Convention is an 1875 treaty establishing international cooperation on units and measurement standards, administered through permanent international institutions.

International System of Units: The globally used system of measurement units, built around seven defining base units. The treaty’s institutions maintain and coordinate the standards underlying this system.
Metric system: A decimal system of measurement based on units such as the metre and kilogram. The convention internationalized cooperation around the metric system’s standards.
Metre Convention member states: Countries that have joined the Metre Convention and participate in its governance and work. Their representatives fund and direct the treaty’s international measurement institutions.
International Committee of Weights and Measures: An informal English name sometimes used for the International Committee for Weights and Measures. It illustrates how the convention’s institutions are cited under variant English translations.
International Bureau of Weights and Measures: An international organization that coordinates scientific work on measurement standards. The treaty established this bureau as its permanent scientific and administrative center.
International Prototype Metre: A platinum-iridium bar that served as the international reference for the metre from 1889 to 1960. The convention’s early work established an international prototype to standardize the metre.
CIPM Mutual Recognition Arrangement: An international framework for recognizing national measurement standards and calibration capabilities. It extends the convention’s cooperation into formal recognition of measurement results.
2019 revision of the SI: A revision that defined several SI units using fixed values of fundamental constants, effective 20 May 2019. The treaty’s institutions coordinated this transition away from selected physical artifacts.
General Conference on Weights and Measures: A diplomatic conference where member states decide on international measurement standards. It is the convention’s principal decision-making body.
International Prototype Kilogram: A platinum-iridium cylinder that served as the international reference for the kilogram from 1889 to 2019. It was a central physical standard produced under the convention’s system.

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