Principles of changeover

In this page we set out some basic principles which we feel should underlie the process of completing the metric changeover:

Think metric! Don't convert

One of the lessons from the experience of countries which have successfully adopted the international metric system is that the transition is best achieved if people are encouraged to think and work in metric measures from the outset without attempting to convert from imperial.

Although the provision of conversion charts can help people initially to gain confidence in using metric, they can also prove to be a hindrance if they are retained indefinitely. This is because people have continued to visualise the familiar imperial measure and then have more or less painfully expressed this in the equivalent metric unit. It is rather like attempting to communicate in a foreign language by continually referring to a dictionary, and it is little wonder that some people have rejected this laborious process and have become resistant to metric units.

Experience has shown that it is far simpler and quicker just to set aside imperial units and to learn to visualise and use metric units without the intermediate stage of converting from imperial.

Phase out supplementary indications

The UK Government's approach to metrication has been characterised by extensive use of "supplementary indications" - that is, giving the imperial equivalent to the primary metric measure. This practice is consistent with the European Union’s Units of Measurement Directive (181/80/EEC), which now "authorises" supplementary indications indefinitely, subject to a review in 2019.

However, the biggest problem with supplementary indications has been that dual pricing has given no incentive to either traders or customers to adapt to change and to think in metric. Assurances were given to Parliament by nervous Ministers that customers could continue to order goods in imperial measures, and the trader would simply translate the imperial quantity into the metric equivalent when pricing the goods. The Government accepted little or no responsibility for attempting to educate the general public. The result appears to have been that metric measures and prices have been widely ignored by large sections of the general public. Consequently there is little understanding that metric units are the primary system in the UK, and a handful of recalcitrant market traders and small shopkeepers persist in weighing in units that are no longer legal for trade.

Experience in other areas has been similar. The publication of weather reports and forecasts in both metric and imperial (e.g. temperatures in both Celsius and Fahrenheit) or a mixture of the two (e.g. visibility in metres but rainfall in inches) has done nothing to further the public understanding or use of metric. (Even worse has been the use of 'Celsiheit': when the media report low temperatures in Celsius but high temperatures in Fahrenheit!)

Similarly, the media have not helped the situation by routinely reporting foreign news stories either in imperial measures only (even when the original source is metric) or in metric measures with imperial equivalent. It is as though news editors (or individual journalists) have assumed that their readers are incapable of understanding metric units and are not prepared to contribute to their education.

For all these reasons, therefore, UKMA is not generally in favour of supplementary indications and does not wish to see their use extended to other fields such as road signage. Rather UKMA favours a "clean break" approach whereby traders, customers, readers, motorists and so forth simply adjust "overnight" to the new system and use it exclusively - just as we now do when we go on holiday or business abroad.

Following the decision of the EU to "authorise" supplementary indications indefinitely, it would not be possible for the UK Government to ban them (even if it wanted to), but it could and should discourage their use, particularly by setting a good example.

Avoid (or minimise) transitional periods

It follows from the last point that UKMA does not generally favour transitional periods during which dual systems are in use - except where a genuine case can be made on practical grounds, such as the time needed to re-equip factories, replace scales, train staff or change road signs. The experience of other countries has shown that, provided that there is adequate government support, persons within the normal intelligence range can adjust to a new system in a few days.

As described above, the UK's programme of adoption of the metric system has been exceptionally slow when compared with that of other countries. UKMA considers that most of this delay has been time wasted - attributable mainly to successive politicians' attempts to postpone potentially unpopular decisions until after they have left office.

UKMA therefore believes that transitional periods during which dual systems are in operation should be as short as possible unless there are very exceptional grounds. This is in accordance with the "clean break" philosophy outlined above.