The imperial system of units, imperial system or imperial units is the system of units first defined in the British Weights and Measures Act 1824 and continued to be developed through a series of Weights and Measures Acts and amendments.
Metrication or metrification is the act or process of converting to the metric system of measurement. All over the world, countries have transitioned from local and traditional units of measurement to the metric system. This process began in France during the 1790s, and has persistently advanced over two centuries, accumulating into 95% of the world officially only using the modern metric system. Nonetheless, this also highlights that certain countries and sectors are either still transitioning or have chosen not to fully adopt the metric system.
United States customary units form a system of measurement units commonly used in the United States and most U.S. territories, since being standardized and adopted in 1832. The United States customary system developed from English units that were in use in the British Empire before the U.S. became an independent country. The United Kingdom's system of measures was overhauled in 1824 to create the imperial system, which was officially adopted in 1826, changing the definitions of some of its units. Consequently, while many U.S. units are essentially similar to their imperial counterparts, there are noticeable differences between the systems.
The pint is a unit of volume or capacity in both the imperial and United States customary measurement systems. In both of those systems it is traditionally one eighth of a gallon. The British imperial pint is about 20% larger than the American pint because the two systems are defined differently. Almost all other countries have standardized on the metric system, so although some of them still also have traditional units called pints, the volume varies by regional custom.
Metrication is the process of introducing the International System of Units, also known as SI units or the metric system, to replace a jurisdiction's traditional measuring units. U.S. customary units have been defined in terms of metric units since the 19th century, and the SI has been the "preferred system of weights and measures for United States trade and commerce" since 1975 according to United States law. However, conversion was not mandatory and many industries chose not to convert, and U.S. customary units remain in common use in many industries as well as in governmental use. There is government policy and metric (SI) program to implement and assist with metrication, however there is major social resistance for further metrication.
The stone or stone weight is an English and British imperial unit of mass equal to 14 pounds (6.35 kg). The stone continues in customary use in the United Kingdom and Ireland for body weight.
The "Plan for Establishing Uniformity in the Coinage, Weights, and Measures of the United States" was a report submitted to the U.S. House of Representatives on July 13, 1790, by Secretary of State Thomas Jefferson.
The Metric Martyrs was a British advocacy group who campaigned for the freedom to choose what units of measurement are used by traders. The group believed that vendors should have the freedom to mark their goods with imperial weights and measurements alone. This opposes the current legal position that imperial units may be used so long as metric units are also displayed.
The Fair Packaging and Labeling Act is a U.S. law that applies to labels on many consumer products. It requires the label to state:
The spread of metrication around the world in the last two centuries has been met with both support and opposition.
Metrication in Canada began in 1970 and ceased in 1985. While Canada has converted to the metric system for many purposes, there is still significant use of non-metric units and standards in many sectors of the Canadian economy and everyday life today. This is mainly due to historical ties with the United Kingdom, the traditional use of the imperial system of measurement in Canada, proximity to the United States, and strong public opposition to metrication during the transition period.
Metrication in Australia effectively began in 1966 with the conversion to decimal currency under the auspices of the Decimal Currency Board. The conversion of measurements—metrication—commenced subsequently in 1971, under the direction of the Metric Conversion Board and actively proceeded until the Board was disbanded in 1981.
Metrication, the process of introducing the metric system of measurement in place of imperial units, has made steady progress in the United Kingdom since the mid-20th century but today remains equivocal and varies by context. Most of government, industry, commerce, and scientific research use the metric system. Imperial units are officially used to specify journey distances, vehicle speeds and the sizes of returnable milk containers, beer and cider glasses, fresh milk is often still sold in multiples of pints, with the metric equivalent also marked, and precious metals are sold by the troy ounce. Metric units must be used when selling other packaged or loose goods, and imperial units can stand alongside the metric units, but it cannot stand out more than the metric units. Imperial units are also often used to describe body measurements and vehicle fuel economy. The national curriculum requires metric units and imperial units that still remain in common usage to be taught in state schools.
Metrication in the Republic of Ireland happened mostly in the 20th century and was officially completed in 2005, with a few exceptions.
Both the British imperial measurement system and United States customary systems of measurement derive from earlier English unit systems used prior to 1824 that were the result of a combination of the local Anglo-Saxon units inherited from Germanic tribes and Roman units.
As of 2009, the European Union had issued two units of measurement directives. In 1971, it issued Directive 71/354/EEC, which required EU member states to standardise on the International System of Units (SI) rather than use a variety of CGS and MKS units then in use. The second, which replaced the first, was Directive 80/181/EEC, enacted in 1979 and later amended several times, which issued a number of derogations to the United Kingdom and Ireland based on the former directive.
The Metric Conversion Act of 1975 is an Act of Congress that was signed into law by U.S. President Gerald Ford on December 23, 1975. It declared the metric system "the preferred system of weights and measures for United States trade and commerce", but permitted the use of United States customary units in all activities. As Ford's statement on the signing of the act emphasizes, all conversion was to be "completely voluntary". The Act also established the United States Metric Board with representatives from scientific, technical, and educational institutions, as well as state and local governments to plan, coordinate, and educate the U.S. people for the Metrication of the United States.
The Weights and Measures Act is a Canadian law governing the units of measurements used in Canada.
The following outline is provided as an overview of and topical guide to the metric system:
The imperial and US customary measurement systems are both derived from an earlier English system of measurement which in turn can be traced back to Ancient Roman units of measurement, and Carolingian and Saxon units of measure.
