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Metrication in the United Kingdom is the process of introduction of metric units for measurement. The UK is in the currently phasing out the legal status of most non-metric units.

The use of metric units has been legal in the UK for most purposes since 1897. The idea was first discussed by a Royal Commission that reported in 1818 . In 1862, the Select Committee on Weights and Measures favoured the introduction of decimalisation to accompany the introduction of metric weights and measures . A further Royal Commission "on the on the question of the introduction of metric system of weights and measures" also reported in 1869 .

Despite the slow progress of metrication, its sole adoption was first recommended by the Committee on Weights and Measures (Hodgson Committee) in 1950, and accepted by the President of the Board of Trade in May 1965. As a result, metric units have been taught in UK schools since the late 1960s, and certain industries also converted or largely converted decades ago. For example the paper industry converted in 1970, and the construction industry between 1969 and 1972—although certain products continue to be produced to with reference to imperial trade names but made using metric dimensions in the factory; for example, a 13mm thick plasterboard is still often called 'half-inch', even though the measurement is rounded to a convenient metric size and so is now only approximately half an inch thick.

Current usage

An example of metrication on UK consumer products. Two of the four items are purely metric. Milk is sold as "1.136 litres 2 pints". Sausages are labeled "340g 12oz" The UK currently uses a mix of metric and non-metric units for different purposes. The photo on the right shows an example of the current situation for common food products. Milk is frequently sold in multiples of the pint, but with metric units also displayed, as with the 2 Pint milk bottle shown. The salt and tinned beans are purely metric. The sausages are labeled "340g 12oz". By law since 1 January 2000, all loose goods sold by reference to units of quantity have to be sold using metric units, however traditional units may also be displayed. UK government policy is to eliminate by December 31, 2009 almost all non-metric units when used for goods and services sold by quantity. Goods and services sold by a description are not covered by weights and measures legislation. Thus, a fence panel sold as "6 foot by 6 foot" will continue to be legal after 2009 but a pole sold as "50 pence per linear foot" is illegal. Road signs and speed measurement in cars have no schedule to change to metric. Non-metric units allowed by UK law for economic, public health, public safety or administrative use from January 1, 2000 are limited to:

• the mile, yard, foot and inch for road traffic signs, distance and speed measurement,
• the pint for the dispensing of draught beer and cider, and for the sale of milk in returnable containers,
• the acre for land registration, and
• the troy ounce for transaction in precious metals.

Other exceptions include aviation, shipping and rail transport. For example, the foot for aircraft altitude, nautical miles and knots (, ).

Draught beer and cider are the only goods that may not be sold in metric units in the United Kingdom; the only legal measures for these drinks when sold on draught are ⅓ pint (190 ml) (rarely encountered), ½ pint (284 ml) and integer multiples of the latter.

Metric is now the system used in all industries. Products that may appear to be imperial are actually manufactured to metric specifications, using metric drawings and made on metric machines, even if references to imperial units persist in some areas.

The UK military continues to use fractions of an inch to measure amunition caliber.

Costs

The estimated costs of metrication in the UK range from near zero to a 1970 estimate of £5bn (about £50bn in 2002 pounds ) by opponents of the change. True scientific calculations of the potential costs have been fairly rare. A 2005 report pointed to the metrication of the UK's 1m road signs as the major cost . A 1970's study by the UK Chemical industry estimated costs at £6m over seven years, or 0.25% of expected capital investment over the change period (1972 White Paper, 'Metrication' Cmnd 4880).

90% of UK exports go to metric countries, and there are costs to business of maintaining two production lines (domestic in Imperial and export in metric) These have been extimated at 3% of annual turnover by the Institute of Production Engineers, and at £1.1bn (1980) per annum by the CBI.

Opposition to metrication

There has been consistent opposition to the process of metrification from a relatively small group. See Metrication arguments and counter-arguments.

External links

• UK Government Department of Trade and Industry (policy statement)
• British Weights and Measures Association (anti-metric)
• UK metric association (pro-metric)
• Drop the Pint

References

1. English Linear Measures: an essay in origins, by Philip Grierson. 'The Stenton Lecture 1971', University of Reading.
2. The Basis of Measurement: Historical Aspects, by Thomas McGreevy. ISBN 0-948251-82-4
3. The Basis of Measurement: Metrication and Current Practice, by Thomas McGreevy. ISBN 0-948251-82-0

• Metrication
• Economy of the United Kingdom