‘Think metric’. A customary way to success

We look at the metric changeover in the UK construction industry, and some of the posters that were part of it.

The comments that followed our last article included variations on the word “convert” about 25 times, including eight in upper case. There are, of course, occasions when it is necessary to convert, but it is best avoided. So this week, Metric Views takes a look at the metric changeover in the UK construction industry between 1967 and 1975, and the accompanying poster campaign run by the Construction Industry Training Board (CITB) on the theme, “Think metric”.

Imperial measures were less than ideal for construction. Setting out was done in feet, inches and eighths, with risks of error during addition and subtraction. Levelling however was done in feet and hundredths. Excavations were measured in feet and inches, but volumes were calculated in cubic yards, without calculators. Laboratory work may have been done in metric, but design calculations were in Imperial. Readers who worked in construction during the 1960s can probably add to this list.

So in 1965, when the UK Government said that they “consider it desirable that British industries on a broadening front should adopt metric units”, there was widespread agreement in the construction industry that it should aim to be at the head of the queue.

Preparation was thorough. Standards, design codes, publications, university and college courses, qualifications, training, publicity, product development, modular co-ordination, the supply chain, and so on – all received consideration. An agreed timetable was published in 1967.

Clearly the workforce would play a key part in the success of the changeover, and the CITB was commissioned to devise a poster campaign with twin themes: ‘Think metric’, and ‘Use millimetres’.

The importance of ‘thinking metric’ during a changeover from older measures had long been recognised, but an emphasis on millimetres was unusual. However, the construction industry had concluded at an early stage that the use of the centimetre should be avoided. Among the reasons was the fact that using the centimetre risked error from misplacing or omitting the decimal point, with 1/8 inch and 1/100 foot both being about 3 mm. The CITB also foresaw that anyone unfamiliar with the metric system might see the centimetre as the metric version of the inch, and would tend to use it unless encouraged otherwise.

Our first two posters show both of the campaign themes. The five postage stamps in the left hand poster are each dimensioned “20 mm”.









Our third poster would perhaps be controversial today – it shows how attitudes have changed over the past 45 years, and clearly belongs to a bygone era. But it also underlines the ‘Use mm’ theme. Even today, the general public might expect to see centimetres if such statistics appeared in metric measures.


In 1961, the Meteorological Office switched internally from Fahrenheit to Celsius, and in 1962 started issuing public forecasts in dual units. But, although science had been metric since 1900s, many industrial processes still used F. So it is understandable that the CITB would wish to draw attention to a temperature scale that might be unfamiliar. It is surprising, however, that there are still people in the UK today who claim Celsius is unfamiliar!


And finally, here is a play on words that might be appreciated by someone who had spent the day working in the sun on a building site. We shall be returning to the idea of ‘Drink metric’ in a future article.


The metric changeover in the construction industry was a success, and was largely completed on programme. The benefits were quickly felt. As an example, UK consultants such as Arup and Fosters went from strength to strength in an increasingly metric world.

So here is a paradox. All new roads in the UK for the last 45 years have been designed in metric, generally for speeds of 50, 60, 70, 85, 100 and 120 km/h. But just before completion of construction, Imperial signs for distance and speed are installed. Furthermore, almost all the vehicles on UK roads today have been manufactured to metric designs, with those intended for the UK fitted, uniquely, with RH drive and an mph option on the speedo. Yet the metric is largely hidden from the driver, who could be forgiven for thinking that little has changed in this respect for 50 years.

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63 Responses to ‘Think metric’. A customary way to success

  1. Jake says:

    @ JFL:

    I am sure British drivers would also quickly 'wise up' to the 'technicality' you draw attention to. The use of 'kph' is borne of ignorance of the proper way to write 'kilometres per hour'. It is as wrong as MpH, M/h or any other variation on a theme would be for miles per hour in the UK (the Americans often write M.P.H., I believe). It is no more the product of an 'unregulated living language', as a poster above calls it, than the spelling 'accomodation' is. That particular misspelling was very prevalent for years and years in British tourist resorts. That did not make it correct. And English 'is' a regulated language, unless you wish to invent your own spellings (though words with alternative spellings do exist of course). But I diverge. As another aside, I had a speeding ticket in Flanders once which showed my speed in 'km/u' (kilometers per uur). If SI applies in Flanders (and it does of course), that should have been km/h. However, not wishing to launch a legal battle with the Flemish authorities, and accepting that I had been speeding, which is more to the point, I paid up at once.

  2. Charlie P says:

    You said "The use of ‘kph’ is borne of ignorance of the proper way to write ‘kilometres per hour’."

    You are wrong, it is normal English usage, and is fully documented, and accepted as such, in all the mainstream English dictionaries that I could find (unlike misspellings such as 'accomodation')

    It is true that the SI brochure frowns upon the use of such abbreviations in "scientific and technical papers", which is fair enough, but that is an entirely different kettle of fish to normal everyday English usage.

    And no, English is not regulated; French is, and I believe some other languages are, but English is not. There may be certain conventions and recognised spellings, but these change as usage develops. There is no body or committee deciding what can and cannot enter into mainstream usage (which does exist for French). The dictionaries follow and reflect usage, they do not prescribe it. If usage of 'kph' ceases some day, then the dictionaries will eventually reflect that, but for now it is undeniably acceptable current usage.

  3. Jake says:

    @ Charlie P

    Yes, you will find 'kph' in dictionaries, reflecting usage, as you say. The Concise Oxford dropped the entry some years ago when I pointed out to them that their book cover called the dictionary 'the most authoritative dictionary in the English language'. It is true that people quickly turn to their dictionaries to prove a point, as you do, but unless a dictionary is genuinely authoritative it merely shows how people use words rather than how they should use them. That includes both spellings and symbol use. That dictionary now only lists km/h. Admittetly, I have not made a point of writing to all dictionary publishers. English is regulated by use, but that does not mean that anything goes. As for your continued insistence upon upholding the validity of 'kph', I can see no logical reason to support a mis-symbol when a real one exists. And please do not repeat that 'kph' is an abbreviation not a symbol; I know your view on that. I doubt whether that distinction is understood among the public at large. That is why people often write metric speeds as e.g. 'xxx kph'. They can be forgiven for thinking that is correct if they see the symbol incorrectly written all over the place. But extensive incorrect usage does not make it correct, as extensive incorrect spelling of words does not make those spellings correct either.

  4. philh says:

    To return to the subject of the original article, whilst it was a good thing to encourage people to think metric, I would not agree with the approach taken by CITB.

    The poster featuring the human foot reinforces the myth that the imperial unit of the same name is representative of its size and a convenient way to visualize it. The measurement unit is significantly longer than a typical human foot.

    The bikini poster sends entirely the wrong message because it encourages soft conversion with no regard to the accuracy of the original measurement. The figure of 914 mm implies that the original measurement in inches was accurate to 1/25th of an inch.

    More generally, in order think metric properly, it is important to learn to visualize the world in convenient rational numbers. In the case of the lovely lady, 900, 600, 900 would probably be adequate.

    The exclusive use of the mm rather than cm is a good idea in the right context but its advocacy has led to some common misunderstandings, e.g. that cm is not an SI unit.

  5. Martin Vlietstra says:

    Another useful exercise is to identify a road in your home area which is one kilometre in length. This is a simple exercise for Her Majesty - she need only go onto the balcony of Buckingham Palace and look up The Mall (or should that be "The Royal Kilometre"?) - measurements made using Google Earth suggest that the distance from the middle of the Victoria Memorial to the far side of the central arch in the Admiralty Arch is exactly one kilometre.

  6. Leo says:

    @Philh I agree on the foot, anyone with feet of approximately a foot long would have serious trouble buying shoes!

    As for that bikini poster, sizes in millimetres are nonsensical. First of all it implies an accuracy that is not realistic, and the numbers are way too big for any meaningful use. That’s why clothing sizes tend to be given in centimetres. Look at this H&M size guide for instance: http://www.hm.com/nl/sizeguide/sizeguide_ladies All measures are in centimetres except occasionally inches for jeans, probably because they are an American invention.

    I think the only place where millimetres might come in handy would be in shoe sizes where that level of accuracy might some times be relevant.

  7. Sven G says:

    Actually, S, M, L, XL and so on (of "American" origin?) probably are more intuitive for clothing: they should be adopted by the SI 😉 🙂

  8. Charlie P says:

    The current Concise Oxford gives "km/h (also kph): abbr. kilometres per hour." The definitive full OED gives "k.p.h. n. kilometres per hour." So kph is fully endorsed as current usage by the most authoritative dictionary of English usage. Hence it is by definition correct usage - what more can I say!

  9. Martin Vlietstra says:

    One of the objections to metrication in the early years was the excessive use of millimetres. The start of the British metrication program was in 1965, only five years after the introduction of SI. The EEC (as it was then) was getting to grips with SI and in 1971 published Directive 71/354/EEC making SI the legal system of measurement within the EEC rather than CGS-based and gravitational-based systems of units. This required the discarding of a host of non-SI "metric " units including the poise, erg, dyne, standard atmosphere, Pferdestärke (also paardekracht, cheval vapeur and cavallo vapore), calorie, kilogram force and many others. (The directive can be viewed at http://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:31971L0354&qid=1441144704069&from=EN). Like the EEC, the British Metrication Board was sailing in "unchartered territory" in judging how best to handle SI and whether or not the prefix "centi-" would die a natural death.

  10. Jake says:

    @ Charlie P who wrote: "So kph is fully endorsed as current usage by the most authoritative dictionary of English usage. Hence it is by definition correct usage."

    Listing a term in a dictionary is not the same as endorsing it and it certainly does not make it correct or preferred usage. You are right in saying that kph is included as it is 'used' as an abbreviation. I have no problem with that argument. But the problem is that the people who 'use' that abbreviation (e.g. journalists) are often the people who do not know that there is a proper symbol for kilometres per hour. I am not aware of this problem existing outside of the English speaking world. If metric usage on road signs were properly established in the UK, people would, I am quite sure, not be writing kph.

  11. Martin Vlietstra says:

    CharlieP wrote "So kph is fully endorsed as current usage by the most authoritative dictionary of English usage. Hence it is by definition correct usage – what more can I say". I remenber reading that somebody in Ireland got a speeding fine quashed because the ticket read "kph", not "km/h", so I checked what Google had to say. When I applied the filter "kph site:.ie", I got 68,000 hits, many of which were related to a construction company KPH. Applying the filter "km/h site:.ie", I got 1.1 million hits. This suggests to me that "kph" is not accepted in legal circles.

  12. Charlie P says:


    In English, dictionaries do not endorse use, they simply document it. The entry is evidence of common usage - and who are we to judge that usage as correct, or otherwise?

    The only time we should be critical of usage is in technical scientific and engineering reports and papers. Journalists are not tied by the SI style guide, which as the SI brochure puts it, is for "scientific and technical papers".

    And what makes you think that metric road signs would make much difference in the UK? Australians, Canadians, Irish, New Zealanders all also commonly use non-SI-endorsed abbreviations such as "kph". And it isn't only English speakers that treat the SI brochure with the contempt its inflexibility brings on it. It isn't hard to find "k" (kilometres) and "kilos" (kilograms) being used in other languages too.

    If we are to progress, we must accept that insisting that everyone adopts that unrealistically inflexible writing style is a non-starter.

  13. Michael Glass says:

    Charlie P showed that the Concise Oxford Dictionary gave first place to km/h. This means that km/h is preferred over kmh. The fact that the OED gives k.m.h. demonstrates that it is behind the times.


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