A system of weights and measures established for the British Empire in 1824 by “An Act for ascertaining and establishing Uniformity of Weights and Measures” (5 George IV chap. 74). The word “imperial” was first used in this connection in a committee report of March 31, 1821. Imperial measure was supposed to take effect on May 1, 1825, but it proved impossible to manufacture and distribute standards to the various cities and colonies by that date, so its implementation was delayed until January 1, 1826 (by 6 George IV chap. 12, 1825).
For the units and their relationships see these tables:
See also: facsimile of contemporary printing of the law; history of the yard
In a characteristically British fashion—especially in comparison to the French reforms 20-odd years before—the new system mainly redefined old measures instead of creating entirely new units, arguably with the exception of the gallon. For the changes made by imperial measure in a particular unit, see the entry for that unit.
The Weights and Measures Act of 1963 enjoined the Board of Trade not “to cause the exclusion from use for trade of Imperial in favour of metric units of measurement, weights, and measures,” but in the 1970s and 1980s imperial measure was tentatively and gradually dismantled in favor of metric units, as the United Kingdom became more integrated with the European Community and its regulations. As a concession from the EC, the mile will be retained on road signs, and the pint in pubs.
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Last revised: 6 October 2006.