How the UK created a measurement muddle

The series of four articles on the outcome of the EU referendum continues with a look at how the current measurement muddle came about.

Britain is no stranger to the benefits of both a single system of measures and an international one. Problems came with reconciling the two when the British Empire declined and with it the use of its measurement system for international trade.

Further back in history, during the Roman occupation, 43 to 410 AD, Britain was part of a common market that extended from the Middle East to the Atlantic, including North Africa, the Balkans and much of Western Europe, and that used a single measurement system, some of whose units are with us today in particular the pound and the mile. And in the Middle Ages, English rulers supported with varying degrees of success a single system of measures, in particular King Edgar who decreed in AD 965 that “Only one weight and one measure shall pass through the King’s dominions”, and the Barons who in 1215 inserted a similar wording into Magna Carta.

Although British scientists contributed significantly to the development of the metric system in the nineteenth century, formulating units for electricity, energy and power, it was not until 1898 that metric became legal for all purposes – 32 years after the USA, but better late than never!

Progress with the adoption of metric measures in the UK in the first half of the twentieth century was slow, but a significant step occurred in 1939 when the Ordnance Survey, the Government mapping agency, began the changeover to metric scales. However, in 1965, the Government signalled in a reply to a Parliamentary question that the changeover in industry should begin in earnest. It noted that half of Britain’s exports were to metric countries and that proportion was likely to increase. It added that it hoped “that within ten years the greater part of the country’s industry would have effected the change.”

From then on progress was swift. Pharmacies, for example, went metric in March 1969 and liquid medicines came with a 5 mL spoon. The construction industry began planning the changeover in 1967, standards began to appear in 1968, metric projects first hit the drawing boards in 1969, and the changeover was substantially complete in 1975. The Government quickly realised that the change affected not just industry, but the whole economy, and in 1969 the UK Metrication Board was created to provide co-ordination. The introduction of decimal currency in 1971, supported by a widespread government publicity campaign, simplified the teaching of arithmetic in schools, and in 1974 primary schools dropped the conversions that were a feature of the Imperial measurement system. The UK was also able to adopt directly SI, the modern version of the metric system, one of the first countries in the world to do so.

There was, however, an early indication of trouble ahead. A provisional date of 1973 for the conversion of road traffic signs had been proposed by the Metrication Board, but as the date approached it was confirmed that the project had been postponed and that “the Government had no other date in mind.”

Elsewhere, the changeover continued steadily through the 1970s, a significant step being the move from rational Imperial to rational metric packaging for household staples such as tea, sugar and flour. By 1978, voluntary conversion had almost run its course, and it was time for the Government to bite the bullet, and require the use of metric measures for foods such as green groceries, meat and fish. With an election in the offing, this decision, like that for road traffic signs, was postponed, and in 1979 the new Government dropped all plans for an orderly changeover and abolished the Metrication Board.

For the next fifteen years, progress continued if slowly, for example petrol pumps went metric during the early 1980s as the price of fuel approached £1.99 / Imperial gallon. In the UK’s automotive industry, several companies went bust or were taken over by foreign car makers, thereby eliminating pound-inch units. However, much of UK economic activity remained resolutely Imperial. This was not so elsewhere in the world, and many Commonwealth countries, such as Australia, Bangladesh, India, New Zealand, Pakistan, and South Africa pushed on with and completed the changeover. By the turn of the century, around 90% of the UK’s trade was with metric countries. Canada like the UK allowed the process to stall, but unlike the UK changed its road signs but not its construction industry, illustrating the random nature of partial metrication.

Readers who have reached this far may have noticed the absence of any link between the UK’s metric changeover and its membership of the European Economic Community. This would change in 1995, and will be the subject of the next article in this series.

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6 Responses to How the UK created a measurement muddle

  1. Daniel says:

    "A provisional date of 1973 for the conversion of road traffic signs had been proposed by the Metrication Board, but as the date approached it was confirmed that the project had been postponed and that “the Government had no other date in mind.”"

    What was the reason for the postponement other than the possibility that a metric hater was running the DfT? The thinking of this person might have been that if he could stop road sign metrication he could stop further metrication elsewhere and possibly even reverse what has already be achieved.

    Editor. The culprit is identified in an article posted on Metric Views in November 2012, entitled 'Surprise choice for transport'.

  2. Charlie P says:


    As far as I know, the mass-volume British motor industry had metricated by the end of the 1970s - although you failed to mention that. As a matter of curiosity, can you list for us the several UK motor industry companies that were still designing in pound/inch units as late as 1980 and subsequently "went bust or were taken over by foreign car makers"?

  3. John Frewen-Lord says:

    It is not quite correct to say that Canada's construction industry did not convert. The ICI (industrial, commercial and institutional) sectors almost completely converted in the late 1970s/early 1980s. I was there, and as a QS worked in this industry. Many government departments (e.g. Ontario Ministry of Health) would only sanction metric projects, while Canada's national building code (a model code that the provinces had to adopt, usually with additions or modifications) is completely metric and remains so to this day.

    It is a different story in the residential sector. While I do know of one house builder who converted his house designs to metric units (when sheet goods such as drywall and plywood were easily available in metric as well as imperial), he was a lone exception, and his houses today are a bit orphaned now that metric sheet goods are no longer freely available (all houses in Canada are wood framed, and therefore compatibility between sheet goods sizes and stud or joist framing centres). Currently the ICI sector now sees a mixture, although I believe plans for new buildings must still be in metric units when submitted for building permits.

    For this (partial) regression back into imperial units we can thank Brian Mulroney, who, paralleling Margaret Thatcher, abolished the Canadian Metric Commission, and, of course we must not forget the influence of the USA, who, once FTA/NAFTA kicked in, objected to Canada's metric-only regime - and got its way.

  4. philh says:

    This very interesting article illustrates the problem politicians and the public have with the perception of what it takes to adopt a system of measurement units and the role they play in society.
    Measurement units are an integral part of communication and trying to use two incompatible systems is like trying to speak randomly in different languages. We can do it but it is wasteful, awkward, can cause misunderstanding and serves no useful purpose.
    The prevailing attitude seems to be that it is easy to teach metric in early education and then let the more mature students learn to cope with imperial when they are ready. So, according to this point of view, it doesn't matter how long it takes for imperial to fade out naturally.
    All this is illustrated by the mere fact that UK governments continue to resist the conversion of road signs and the public have not put pressure on them to do so. The point being missed is that if we keep imperial on public signs the expected decline will not happen and future generations will be condemned to endure the present unsatisfactory nonsense.

  5. Martin Vlietstra says:

    When Belgium was invaded in 1914, their main cartographic office based in Antwerp managed to decamp to the UK with all the master copies of their maps. Unsurprisingly, these maps used metric units, but once in the UK, an imperial-based grid was superimposed on the maps for the benefit of British artillery commanders.

    Between the wars the War Office experimented with various grids and in particular the metric Cassini Grid of 1927 proved the most useful. This grid, similar to the current Ordinance Survey National Grid, used a meridian through the Isle of Wight as its principal meridian. Anybody visiting the War Cabinet rooms can see such a map hanging up. In 1938 a start was made on revising the grid and the current OS grid was designed. The current grid used 2° W as its principal meridian. This meridian passes through Poole Harbour.

  6. Michael Glass says:

    One good outcome of the British attempt to metricate was that it prompted Australia to change. The only difference was that we went ahead and our metrication was much more thorough than what happened in the UK.


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