Imperial units and decimals. Not a winning combination.

The signing of the Metre Convention on 20 May 1875 by 17 nations, including Austria-Hungary, France, Germany, the Ottoman Empire, Russia and the USA, sounded the death knell of the imperial measurement system. In this article, Ronnie Cohen looks at an earlier proposal that was intended to make this system better fit for purpose.

In support of the retention of imperial units, it is claimed that binary subdivision, divisibility by three and the use of base 12 are more convenient. Though there are arguments in favour of bases other than 10, the imperial system uses many that have little to recommend them.

The report of the Parliamentary Select Committee on Weights and Measures of 1862 argued that it would be an obvious improvement to reduce all these bases to some harmonious form. The first question that arose was whether that form should be binary, decimal or duodecimal. One option that was seriously considered by the 1862 Committee was the decimalisation of imperial units, along with the decimalisation of the UK currency.

The 1862 Committee examined three options for the future use of measurements within the UK. These were:

  • Retain the present system.
  • Create a distinct UK decimal measurement system.
  • Adopt the metric decimal system, in common with other countries.

Among the witnesses who appeared before the Select Committee, hardly any defended the present system established by the Act of 1824. The report of the Committee pointed out “that the best proof of the insufficiency of the present system for all the practical purposes of life is found in the adoption of so many systems better suited to their wants, by different classes of the people”.

It went on to say, “The superiority of a decimal system has long been acknowledged. Our engineers have, for a considerable time, made use of one. The decimal measuring-chain and decimal levelling staff are instruments familiar to them. Insurance companies have long employed decimals. The Equitable Insurance Company have kept their ledger on the pound and mil system for a hundred years.”

The Committee noted that, as the imperial measurement system was found to be inadequate, other systems were adopted that were more suitable to the task in hand, such as decimally computed grains for scientific purposes, bullion weights that used decimal multiples and divisions of the troy ounce, decimal coal weights, and the occasional use of the metric system for scientific use. There were other practical uses of decimal systems used with imperial units. In the manufacture of guns, the measurements used were in thousandths of inches. The Master of the Mint told the 1862 Committee that they used the decimal system at the Mint by dividing the troy ounce into tenths, hundredths and thousandths.

The report of the Select Committee continues, “The decimal scale, however, appears to us to be by far the most convenient for all transactions which become the subject of written accounts, and for all transactions, of whatever kind, in which great numbers of weights and measures are combined by addition or multiplication.”

Here are some quotes from the Select Committee report, recommending the decimalisation of some imperial units:

  • “We beg particularly to indicate the decimal subdivision of the foot (which is even now usually engraved on foot rules and levelling staves), as one extensively used in the practice of engineers, and one which we would recommend for the recognition of Government in every case.”
  • “That the name milyard, or some other to be fixed by Act of Parliament, be recognised as describing the measure of 1000 yards, without the necessity of further definition.”
  • “That the only legal weights above one pound be, weights of multiples of 1 lb, not exceeding 10 lb; and weights of 10 lb and its multiples, not exceeding 100 lb. That the name ‘centner’, or some other be to fixed by Act of Parliament, be recognised as describing the weight of 100 lb, without the necessity of further definition.”
  • “It has been proposed to make a stone 10 lb, a hundredweight 100 lb, to make 10 ounces in a pound, and to create a lower denomination, of which there should be 10 in an ounce.”

One member of the Select Committee, even suggested that the yard should be redefined as the length of a metre and the mile should be redefined as the length of a kilometre, and that they should be called the new yard and the new mile!

In an 1857 paper on standard decimal measures of length, Joseph Whitworth said, “I have long been convinced that great and rapid progress would be made in many branches of the mechanical arts if the decimal system of measures could be generally introduced. To state the case broadly, instead of our engineers and machinists thinking in eighths, sixteenths and thirty-seconds of an inch, it is desirable that they should think and speak in tenths, hundredths, and thousandths. I can assure those who have been accustomed to the fractional system that the change to the more perfect decimal one is easy of attainment, and, when once made, it will from its usefulness and convenience amply repay any trouble which may have attended its acquirement.” (Source:

The Select Committee concluded that it would be more beneficial for the UK to adopt the same measurement system that was being adopted by many other countries, and it rejected the creation of a uniquely UK decimal system, saying that “… it would involve almost as much difficulty to create a special decimal system of our own as simply to adopt the Metric decimal system, in common with other nations; and if we did so create a special national system, we should, in all likelihood, have to change it again in a few years, as the commerce and intercourse between nations increased into an international one.”

Examples of decimal imperial units survived long after the report of the Select Committee had been forgotten. Civil engineers were still using levelling staffs graduated in feet and hundredths until the UK construction industry went metric in the early 1970s, and the thousandths of an inch advocated by Mr Whitworth have lingered in some of the by-ways of UK manufacturing industry right up to the present time. Curiously, the Americans sometimes decimalise the foot as suggested by the Committee – this is a US tape measure:

(A problem with using such a tape is that the tenths of a foot might be mistaken for inches.)

Thanks to US dominance of the aerospace industry after the Second World War, we measure altitude in feet not metres (and certainly not miles and yards) and engine thrust in thousands of pounds as an alternative to kN (but seldom in tons).

Would the extensive adoption of decimal imperial measures, as considered by the Committee, have helped to prolong the system’s life? This seems unlikely – The Metre Convention would soon ensure that imperial’s days were numbered. But the failure to adopt the Committee’s ideas for decimalisation of measures suggests that the imperial system’s survival for a further century was due to familiarity and inertia rather than utility.

A summary of the Select Committee report can be read at:

The full report can be downloaded as a free e-book from:

6 thoughts on “Imperial units and decimals. Not a winning combination.”

  1. Towards the end of the most recent article by Metric Maven, a US blogger, there are details of proposals made in the 1920s for decimalised US measures. The Americans then, like the UK Government in the 1980s, decided that the metric changeover could be achieved voluntarily. Decimalised customary measures were, according to Metric Maven, included in a Bill with the intention killing off any plans to set a cut-off date for the US metric transition. This appears in the article under the heading, “The New System”:
    As the French say: “Everything changes. Always the same thing.”


  2. Derek

    I believe the French saying is: “plus ça change, plus c’est la même chose”—”the more it changes, the more it’s the same thing”, usually translated as “the more things change, the more they stay the same.” The saying is an epigram of Jean-Baptiste Alphonse Karr.

    In a previous post here on Metric Views, there was a discussion on the unified screw thread in the late 1940s. The unified screws were meant first to unify the two different standards used between the US & UK, but despite the UK participating and formulating the standard, they never adopted it. They continued using Whitworth right up to metrication. The Americans were hoping the unified thread would become a world-wide standard, but it never did. Within 20 years everyone but the US were in the beginning years of metrication.

    I believe the US to a major extent and the UK to a minor extent fear change the most. They both pay lip service to change and in the case of the US may even initiate change but often get cold feet somewhere in the process and quit before the change has the opportunity to take effect or provide its true benefits. The UK was able to affect much in the area of metrication but comes short of completing the change and even in areas where change was successful such as in the markets, the population continues to speak and refer to older unit names.

    Metrication failed in the US in the ’70s because of that very French saying. Opponents grabbed headlines with stories that nothing will change but the numbers. A half-inch will still be a half-inch, but it will have to be expressed as 12.7 mm. A pound will still be there, but will have to be referred to as 0.45359237 kg. A journey of 50 miles would become 80.4672 km. Metrication could never result in a change of dimensions to round, sensible numbers as that would result in huge imagined costs. The result is the Americans backed away.

    The US failure to change doesn’t affect just metrication, but even the issuance of money. Whereas everyone else has their unit currency as a coin, the US continues to use paper.

    Resistance to change is the major cause of the US losing its influence in the world. Those who have nothing to lose by moving forward are passing the US & UK by and prospering from it.


  3. The metric system is a closely defined and universally recognised system under the guidance of an international body. The imperial system is a conglomeration of units which form a rough whole. In Great Britain there were five different systems of weight and three of capacity. Until the 1960’s, Commonwealth countries based the value of the units of length and mass on Imperial Standards kept in London, but the U.S.A. had, since 1893, defined its yard and pound on the International Metre and Kilogram. The advantage of the metric over the imperial system is that it is entirely decimal, and being coupled with the decimal system of coinage, it makes for ease in calculation.


  4. I can’t imagine in metric. I can’t imagine 1/1000th the distance between the equator and north pole. I’ve never seen the base unit. I’ve never walked from the equator to the north pole. I can’t imagine how I could do it in a straight line, or how this unit of measure would make sense in my mind when converting cm and mm to to inches, which make perfect sense and thanks to owning 2 thumbs, I’m never without reference. I also own 2 feet, so I always have a reference there too. I can walk and have a good idea about how far 1,000 paces will take me.

    I’m an American and a Civil Engineer. I design things for people and the Earth. Funny thing about the Earth, it’s not a perfect sphere, it’s more of an elliptoid, but it’s not a perfect elliptoid either, so we call it a geoid.

    I have my survey crews takes measurements out in the field based on GPS, mostly, but I still have to calibrate my computer to accurately understand these survey point files in reference to the geoid and calibrate for standard equipment error. Different equipment results with different errors. Meanwhile, my computer understands everything in SI units ands converts my feet and inches into SI units.

    I live and work in Texas. Texas is a big State. We measure land in sections here (1 mile square) for good reason, because 120+ years ago surveyors (working for the rail roads) came through here and measured everything based on sections in US Survey feet, and all of our legal descriptions for real estate are based on these old surveys, unless they were based on even older Spanish or Mexican surveys that were using “varas” as their base unit of measure. A “vara” is a Spanish yard, or about 33″, fyi.

    Thing is… the cross sectional latitudinal radius of the earth changes as you move north or south away from the poles, so for the northern hemisphere this means that the north end of the property is slightly shorter than the south end, which means the bearings describing the eastern and western boundaries are slightly different. This different becomes more exaggerated the further from the equator too.

    I deal with measurements extensively everyday of my life, and I can understand how metrics is valuable as a sort of Rosetta stone for all customary units of measure, but @ the end of the day, my computer makes the unit conversions for me from a huge range of measurement systems: degrees latitude/longiture, meters, feet, varas, inches& then it scales my designs to print copies. All of this would be a horrendous pain in the ass if it were not for computers, but now we have computers, and converting between units is easy and flawless. Why bother forcing people to use metrics in their daily lives, when traditional units work just as well and are more intuitively understood because they’re based on human proportions and human abilities?


  5. @John Buford
    To those of us that did all that crap before computers were even thought of is the very reason we want the change to metric to happen, and the sooner the better. It is a very naive outlook to assume the computer will always sort the mess out for us. Once again the point is, whats the point? Why use more than one system in the first place? A foot is nowhere near a human foot, an inch nowhere near a thumb, and a stride is nearer a metre than a yard. This is the same nonsense we get in UK from our ‘other lot’. As we on this side of the fence point out the Mars lander, the computers did not do such a good job as the humans forgot to tell them what to do, or to tell them to do it, whatever, it was a disaster. Not doing conversions saves conversion mistakes.
    UK is pretty much metric anyway for most purposes (so the government tell us), apart from roads which is overcome by using a metric sat nav (brilliant!), also beer and doorstep milk in pints is easy overcome by not drinking them, no loss there.
    I wonder how many people in the world (or Texas) know the length of your survey foot? Not many I would suggest.


  6. John Buford,

    But your survey crew can’t use their feet and thumbs in surveys, as different crew members have appendages of different sizes. They in fact have to use standard decimal feet. So what are standard decimal feet? Well, they are either 0.3048 m (International foot) or 1200/3937 m (US Survey foot). I don’t know which foot Texas uses, Michigan uses the international foot, since NAD83 datum. Yes, that’s right. We don’t quite have 50 States = 50 Ways, but each state picks a foot and they didn’t all pick the same. USGS produces all geodetic data in meters, then multiplies by either 1250/381 or 3937/1200 depending on what kind of foot each State likes.

    Since you can’t imagine the meter and the foot (both of them) is/are defined by the meter, does this mean you can’t imagine a foot either, except by looking at your own wrong sized foot? Do you have one Survey foot and one International foot?

    The 1/10000 of the meridian arc definition was original intent but hasn’t been the definition of the meter since 1799. Why belabor a 215 year old definition? (Although as a civil engineer, you might be intrigued by the story of the expedition to attempt to measure that arc)

    About 95% of the people in the world use the metric system as their daily measurement system and they don’t understand your feet and aren’t going to change to them. As various US companies (at least large and multinational companies) metricate, you can be part of a dwindling 5% or join the majority. Do you really think the 5% are going to convince the 95% percent to change? The US’s economic clout in the world has dwindled based on this incorrect belief, as it hurts our opportunity to export, yet people here seem willing to buy cheap, metric Chinese imports.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: