France was the first country to adopt the metric system for commercial use.
The system emerged during the French Revolution as a response to a chaotic patchwork of local measures. Before metrication, France had hundreds of unit names, and the value of a measure could vary from one town or trade to another. Reformers wanted a uniform, decimal system based on reproducible natural standards rather than local custom.
French law formally defined the metric system on 7 April 1795. Scientists then refined the physical standards: the metre was linked to the Earth’s meridian, while the kilogram was based on the mass of water. Platinum prototypes for the metre and kilogram were deposited in 1799.
Adoption was not immediate or smooth. Napoleon introduced a compromise system for retail use in 1812, and the metric system was firmly reimposed in 1837, taking effect in 1840. Thus, “adopted” refers to France’s pioneering legal decision, not instant everyday acceptance.