<P> Some 90% of United Kingdom exports go to metric countries (as only Liberia, Myanmar and the United States have not adopted the International System of Units), and there are costs to business of maintaining two production lines (one for exports to the US in US customary units, and the other for domestic sales and exports to the rest of the world in metric). These have been estimated at 3% of annual turnover by the Institute of Production Engineers, and at £ 1.1 billion (1980) per annum by the CBI . Regardless of United Kingdom metrication, goods produced in the United Kingdom for export to the United States would have still been labelled in non-metric units to comply with the US Fair Packaging and Labelling Act . </P> <P> In 1978 the cost of converting road signs from miles to kilometres in the United Kingdom was estimated to be between £ 71⁄2 and £ 81⁄2 million (1978 prices). A 2005 report pointed to the metrication of the United Kingdom's two million road signs as the major cost of completing the United Kingdom's metrication programme . The Department for Transport (DfT) costed the replacement of all of the United Kingdom's road signs in a short period of time at between £ 565 million and £ 644 million . In 2008--09, before the outcome of the consultations that led to the EU directive 2009 / 3 / EC was known, the DfT had a contingency of £ 746 million for the metrication of roads signs . </P> <P> Traditionally, weights and measures legislation in the United Kingdom only applied to trade, but when the United Kingdom joined the European Economic Community, it had to align its legislation with EEC directives that were in place . These directives included EEC directive 71 / 354 / EEC which related to weights and measures and which required the United Kingdom to formally define in law a number of units of measure, hitherto formally undefined in law including those for electric current (ampere), electric potential difference (volt), temperature (degree Celsius and kelvin), pressure (pascal), energy (joule) and power (watt). </P> <P> Due to public opposition to metrication (a 1979 survey indicated that, of people who knew about the programme, 46% opposed it and 31% supported it), the programme stalled . In the late 1970s, the United Kingdom government asked the EEC to postpone the deadlines for the introduction of metric units . The result was the repeal of directive 71 / 354 / EEC and the introduction of directive 80 / 181 / EEC . This new directive contained a derogation allowing for the continued use in the United Kingdom, until the end of 1989 (subsequently extended to 1995), of many imperial units then in use for trade . The directive should have been transposed into United Kingdom law by 30 June 1981, but this transposition only occurred with the enactment of The Weights and Measures Act 1985, which also removed from the statute book a large number of imperial units of measure that had fallen into disuse as a result of the completed elements of the metrication programme . </P>

When did the uk start using the metric system