This map shows international measuring system of units and the chronology of the advance of metric usage around the world.

Only three countries - Burma, Liberia, and the United States - have yet to adopt the International System of Units as their official system of measurement (weights and measures). Although use of the metric system has been sanctioned by law in the US since 1866, it has been slow in displacing the American adaptation of the British Imperial System known as the US Customary System. The US is the only industrialized nation that does not mainly use the metric system in its commercial and standards activities. At the same time, the US Armed Forces and medical and scientific communities do use metric measurements exclusively (including for nutritional information of consumer goods and drugs), and there is increasing acceptance many other sectors of industry.

Note:

Adoption of the metric system by the various countries, or metrication, is shown by year on the map. France is the first country officially adopted the metric system in 1795.