Metrication

Metrication or metrification is 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.

Since 2006, three countries formally do not use the metric system as their main standard of measurement: the United States, Myanmar, and Liberia. In the United Kingdom metric is the official system for most regulated trading by weight or measure purposes, but some imperial units remain the primary official unit of measurement. For example, miles, yards, and feet remain the official units for road signage – and use of imperial units is widespread. The Imperial pint (expressed in metric units) also remains a permitted unit for milk in returnable bottles and for draught beer and cider in British pubs. Imperial units are also legal for use alongside metric units on food packaging and price indications for goods sold loose, and may be used exclusively where a product is sold by description, rather than by weight/mass/volume. E.g. Television screen and clothing sizes tend to be denominated in inches only, but a piece of material priced per inch would be unlawful unless the metric price was also shown.

Some sources now identify Liberia as metric, and the government of Myanmar has stated that the country would metricate with a goal of completion by 2019. Both Myanmar and Liberia are substantially metric countries, trading internationally in metric units. Visiting advocates of metrication have stated that they use metric units for many things internally with exceptions such as old petrol pumps in Myanmar, calibrated in British Imperial gallons. These and other countries have adopted metric measures to some degree through international trade and standardization for example, Sierra Leone switched to selling fuel by the litre in May 2011. The United States mandated the acceptance of the metric system in 1866 for commercial and legal proceedings, without displacing their customary units. The United Kingdom followed suit in 1897 and did not make the use of metric units compulsory for most purposes until 1995.

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