Which country was the first to employ the metric system?

Metrication or metrification is the conversion to the metric system of units of measurement. Worldwide, there has been a long process of independent conversions of countries from various local and traditional systems. Beginning in France during the 1790s and spreading widely over the following two centuries, but the metric system has not been fully adopted in all countries and sectors.

The metric system was officially introduced in France in December 1799. In the 19th century, the metric system was adopted by almost all European countries: Portugal (1814); Netherlands, Belgium and Luxembourg (1820); Switzerland (1835); Spain (1850s); Italy (1861); Germany (1870, legally from 1 January 1872); and Austria-Hungary (1876, but the law was adopted in 1871). Thailand did not formally adopt the metric system until 1923, but the Royal Thai Survey Department used it for cadastral survey as early as 1896. Denmark and Iceland adopted the metric system in 1907.