Date context
Established through the Metre Convention of 1875
Cooperation established by convention
The Metre Convention signed on 20 May 1875 provided for a jointly maintained International Bureau of Weights and Measures. It enabled cooperation on improving the metric system in response to scientific, industrial and trading needs for comparable measurements.
Standards and comparability
Early work included physical standards such as prototypes for the metre and kilogram, later expanding to other fields. Comparisons and shared methods among national laboratories support checks on measurements expressed in the same units, including their errors and uncertainties.
The evolution of the SI
In 1960 the General Conference on Weights and Measures adopted the name International System of Units and abbreviation SI. From 20 May 2019 definitions rely on fixed numerical values of defining constants, changing the basis for realizing units while preserving continuity in everyday measurements.
Decisions and continuing scientific work
The General Conference, International Committee and Bureau have different responsibilities within the system. The BIPM coordinates and conducts scientific work supporting stable, internationally consistent measurement, while formal decisions and national implementation remain parts of a broader cooperative structure.