Japan ratifies the Convention du Metre in 1886 and in 1890 Japan receives the prototype metre and kilogram from the BIPM (Bureau international des poids et mesures – International Bureau of Weights and Measures). In a law of 1891 (which goes into effect in 1893) the traditional units shaku 尺 and kan 貫 are taken as the fundamental units of length and mass. The use of the metric system is approved and the conversion factors between the systems are fixed. In 1909 the units of the inch-pound scheme are also adopted as legal resulting in three legally approved measuring schemes. The Japanese Diet 日本国の国会 passes a bill making the metric system the unique system in March 1921.

The Imperial Ordinance of 1 July 1924 fixes the date of enforcement of this law, but the Ordinance also permits the use of other units as a transitional measure. The changeover to the metric system takes place in two stages. First stage: government offices, public services, and other leading industries must convert in ten years. Second decade: all the other activities and enterprises must convert. The state changes primary school textbooks in 1925. The change proceeds rather smoothly at the beginning, but opposition becomes furious beyond all reason as the second decade approaches. Opponents of the metric system believe that the adoption of a foreign measuring system would have a bad influence on national sentiment, cause dislocations in public life, needless expense to the nation, prove disadvantageous to foreign trade, and hurt the national language and culture. In reaction, the government in 1933 postpones the date of conversion of the first stage by five years and the date of the second stage by ten years. Opposition to the metric system becomes even stronger after this postponement so the government announces a second postponement. An Imperial Ordinance in 1939 allows shaku-kan to remain in use indefinitely in special cases. After the war due to the presence of occupation armies, sale of gasoline changes from litres to gallons, cloth from metres to yards. Again, Japan is using three schemes. Fortunately, the occupation armies believe that it is reasonable to adopt the metric system.

The Diet passes a new Measurement Law in 1951 that is promulgated in June and enforced on 1 March 1952. It allows the use of shaku-kan and inch-pound schemes until 31 December 1958, the same date set by the old law after two postponements. National and local government officials, scholars, members of the Japan Weights and Measures Association, and other representatives from private organizations join forces and form an unofficial Metric System Promotion Committee in order to prevent any re-occurrence of opposition to metrication. The conversion campaign uses the press, radio, television, and a shower of pamphlets. Japan converts consumer good sales gradually one after the other. As the metric campaign resumes in 1956 the percentages of adoption of the metric system are in electricity, gas, and water supply 95%; in chemical industry 90%; in metal working 80%; machine industry 70%; textile industry 60%; and in other industries 60%. The Diet passes the Metric Unit Law to Coordinate Metric Revisions to Other Laws in 1958 which changes the non-metric units used in other laws and regulations to metric ones. The biggest job in this regard is registration lists of lands and buildings; rewriting starts in 1960 and is completed by March 1969. A letter of 4 December 1981 from the Japanese Standards Association states that the metric system in Japan has been completely adopted with the exception of the capacity of the 1 shoh 升 sake bottle (1.8 litre) and dimensions of Japanese style houses.

12 Jul 2015