Use of the kilometre in the UK

As noted in a comment on our last article, the BBC’s acclaimed new series Blue Planet 2 uses metric measures for smaller distances and depths but miles for greater ones. Ronnie Cohen takes this opportunity to look at instances when kilometres are preferred to miles.

In the UK, miles are generally preferred to kilometres, especially in the non-specialist media. This is probably a consequence of the continued use of miles on road traffic signs, and contrasts with the widespread use of metric measures for shorter distances. However, we are accustomed to using the kilometre in many different contexts in the UK, and this article looks at some of them.


These have been metric for as long as most people can remember. Although the Olympic Games have used metric units since their foundation in 1896, the Commonwealth Games did not adopt metric measures until 1970. The official distance of the marathon is 42.195 km.

Marathon and charity races

Such long-distance races are often advertised as 5K and 10K races. There often seems to be a reluctance to use the symbol for the kilometre – km.

Football (soccer) commentaries

I have occasionally been surprised when Match of the Day has shown the number of kilometres a footballer has run in a game among the statistics. English football remains Imperial, but the rights to broadcast it are sold worldwide and, as with Blue Planet 2, he or she who pays the piper calls the tune.

Rugby football

From 1975, metric measures have been used in the game. For example, the 25 yard line became the 22 metre line.

Fuel efficiency figures

Official fuel efficiency figures for vehicles are expressed as litres per 100 kilometres (L/100 km). The lower the figure, the more fuel-efficient the vehicle. Typical values fall between 4 and 10 L/100 km.

Emission levels

Emission levels are expressed as grams per kilometre (g/km) in car advertisements and reviews.

Driver location signs and marker posts

Driver location signs and marker posts show the number of kilometres from the start of the motorway. These reference markers are used by the emergency services to locate incidents.

Footpath signs


Kilometres are shown on some footpath signs around the UK, either alone or alongside miles. Contrary to the impression created by groups that specialise in vandalising signs, those which have planning permission meet legal requirements whatever units are used.

Media reports

Some newspapers and magazines use kilometres to express long distances in their reports, either alone or alongside miles. However, some national British newspapers appear to prefer miles to kilometres. Usage varies between newspapers. Some have a policy of letting their journalists use what units they like. Television and radio programmes aimed at an international audience that are broadcast in the UK, such as BBC Newsday, tend to use kilometres.

Canal and river navigation signs

Canal and river signs are not covered by the derogation for the continued use of miles, yards, feet and inches on British road signs. So canal and river signs must show kilometres for distances and kilometres per hour for speed limits.

Modern tram and light rail systems

Modern British tram and railway systems such as the Docklands Light Railway (DLR) and the Croydon tram network are entirely metric and use kilometres. As the metric ERTMS signalling system is rolled out over the next 20 years, the use of kilometres will increase on British railways (see for more details).
Diamond-shaped speed signs for tram drivers use a white background with a black border. The black digits that appear on these signs represent tram speed limits in kilometres per hour. These signs are only intended for tram drivers.

Ordnance Survey maps

Ordnance Survey maps use a kilometre-based grid and have used metric scales for over forty years.

Commercial road atlases

Commercial road atlases use kilometre-based gridlines and dual scales. Typically, the scales use both miles and kilometres. Despite the fact that the Ordnance Survey is exclusively metric and is the basis for commercial map makers, dual-measurement road atlases are undoubtedly strongly influenced by the continued use of miles on British roads.

Funfair ride information

Information about funfair rides was given in metric units, including speeds in kilometres per hour. I wrote about this in a previous Metric Views article, which you can find at

High Speed 1

Britain’s only high speed line, HS1, from London St Pancras to Folkestone, has speed limit signs in km/h (shown as “KMH”).

Tachographs and speed limiters for large vehicles

Tachographs use kilometres to record the travel distances for big vehicles. The speed limiters used for big vehicles are based on kilometres per hour, which is incompatible with official speed limit signs on British roads.

Motorcycle tests

Motorcycle tests include an emergency stop at 50 km/h, which is the standard speed limit for urban areas throughout Europe, except the UK of course. You can find out more about British motorcycle tests in a previous MV article at

Documentaries and science programmes

Documentaries and science programmes often use kilometres.

Fitness equipment

The information displayed on exercise equipment at gyms is typically metric. That includes the number of kilometres run on treadmills. Motion speeds (e.g. running, rowing, cycling, etc.) tend to be shown in kilometres per hour.

British legislation and official publications

Official use of measurement units is metric for most purposes with only limited official use of imperial (i.e. road signs, draught beer and cider, doorstep milk and precious metals). This includes the use of measurement units in British legislation. For example, the Commons Act 2006 uses square kilometres for land areas (source: Road traffic volumes are published in both kilometres and miles (source: Government publications also tend to use kilometres.


Speedometers in cars sold in the UK show both miles and kilometres. This is a legal requirement.

Weather visibility

Visibility levels are expressed in metres for short distances and kilometres for long distances. The UK Met Office has been metric for most purposes for over 50 years.

Readers may be able to suggest additions to this list.

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7 Responses to Use of the kilometre in the UK

  1. How can we put pressure on the BBC to use metric measurements? They don't seem to have an editorial policy on this.

  2. Ezra Steinberg says:

    As has been noted in many places British documentaries vary wildly in their use (or not) of metric and Imperial.

    It is hard to know why there is such a mish-mash in most cases since the narration is entirely scripted from start to finish. (What people who are interviewed such as the guest scientists on the show is another matter.) Sometimes once can guess that the primary market for the program in the USA, which could explain the use of Imperial. However, documentaries such as those produced by the BBC are (I would imagine) marketed world-wide, to include countries such as Canada, Australia, New Zealand, and South Africa, which would argue for at least including metric even if it is always given alongside Imperial.

    The latest befuddling head scratcher comes from the otherwise superb and entertaining program with David Attenborough about the British National Museum. For the entire first half of the program Sir David uses only metric. I was ecstatic! Then, suddenly, he switches to Imperial (albeit followed by metric, almost as if the latter were given in virtual parentheses 😉

    Why on earth the sudden switch midway through the program? I cannot fathom a reasonable answer.

    The good news is that once road signs get converted in the UK to metric this whole problem will rapidly disappear given what we know transpired in Canada and Ireland after their road signs were converted to metric.

  3. Daniel Jackson says:

    Speaking of footpath signs, this one might be of interest:

    The BWMA and ARM appear to be on a roll. They damage signs and are treated like heroes.

    Burnely Council supposedly has GIVEN IN and will convert their metric footpath signs to Imperial. ARM even got an article written about them on the front page of the Wall Street Journal.

    There has to be something the UKMA can do to be an effective counter-force. You have to fight fire with fire.

  4. John Frewen-Lord says:

    Some 20-odd years ago, when I lived in Canada, I subscribed to the American publication Car & Driver. One month, the Editor-at-Large commented on his own special page how well USC numbers worked in computing time and distance, in particular the fact that 60 mph equated to 1 mile per minute, and that metric measures offered no such mnemonics.

    Au contraire, I wrote in. In metric, you have the following:

    Short journeys are usually measured in minutes. A good urban/suburban journey can easily achieve 60 km/h (37 mph). Which of course is 1 km per minute. Aunt Agatha's house is 20 km away? Expect to get there in 20 min.

    Conversely, long journeys are usually measured in hours. And a good average on such a journey is 100 km/h (62 mph). Driving the 700 km from LA to San Francisco? Expect it to take 7 hours.

    And to achieve that 100 km/h average speed, including stops at rest areas and the like, you would probably have to be driving at - er hmm - 120 km/h (75 mph, 2 km per minute). The next exit is 12 km away? You'll reach it in 6 minutes.

    The E-at-L agreed with me, to the point that he quoted me personally on his page, and pointed out that, yes, metric units on the roads DO work better than USC.

    Just a pity that, E-at-L of one of America's foremost motoring journals notwithstanding, the USA has made no further advancement in that respect. As of course, neither has the UK.

  5. Martin Vlietstra says:

    When Germany invaded Belgium in 1914, the Belgian mapping service, which was based in Zeebrugge, were able to move their copperplates to the UK. The British army made extensive use of these plates, but had to change the metric grid to an Imperial grid. However they saw the benefit of the metric grid and between the 1920's and the 1940's the War Office developed the "War Office Cassini Grid" which was a forerunner to the current Ordnance Survey grid.

    If you visit the Cabinet War Room in Whitehall from which many World War II operations were directed (now part of the Imperial War Museum), you can see a war-time map on the wall. It clearly has a 10 km grid. The current reference OS north-south grid line (2 degrees West) passes about 900 metres to the west of Brownsea Island in Poole Bay. The Cassini Grid used a different reference north-south line, so one can quickly tell one projection from the other by looking for the closest north-south grid line to Brownsea Island in Poole Bay. The map in the Cabinet War Room employed the Cassini grid, developed in 1927.

  6. jackthesmilingblack says:

    Can I have a ruling on the correct abbreviation for pounds weight?
    So many times I've see "lbs" , but my instinct tell me it should be "lb".
    After all you wouldn't see "10 kgs", now would you?
    Yes, I do read the Daily Mail on line even though I'm banned from contributing. DM editor even threatened to contact my employer. Good luck with that.
    Jack the retired Japan Alps Brit

  7. John Frewen-Lord says:

    We have recently subscribed to Netflix. Not sure if this has been noted before, but Netflix is running a series in their Science and Nature section titled: Precision: The Measure of All Things. I've only watched the first episode so far, but it is very predominantly (but not entirely) metric. Certainly its focus is on defining the metre and the second. Just a pity that its presenter, Professor Marcus du Sautoy, reverts to miles on a number of occasions when describing some distances.


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