Why we won’t kill the Imperial System

Back in grade school, we were told that the Imperial System was a thing of the past, that eventually we’d be living the Metric System life, with all it’s base-10 logic built right in. We’d be just like the rest of the world. But those predictions have proven about as accurate as the flying cars and moon colonies that we all imagined we’d be enjoying in the year 2012.

Occasionally, the issue bubbles up and people argue back and forth about why we haven’t gone Metric, but I think it’s all about inertia. There would be a huge intellectual cost in moving to a new system—training ourselves to think of temperatures in Celsius when we’re leaving home and trying to decide on whether to grab a jacket. Straining to remember what kilometers per liter really comes down to, when we’re used to a lifetime of miles per gallon. Attempting to determine whether you’re losing enough weight, as you stare at the scale showing a strange number of kilograms.

While there are economic costs—heck, just think of the signage issues on our roads—they should be lower today than they would have been a generation ago. Many consumer products in this digital age already allow us to toggle between Imperial and Metric units. And the prevalence of smartphones means that no one has an excuse not to have a conversion app (or at least a calculator) on them at virtually all times.

What this issue comes down to is, as I said, inertia. It’s laziness. No one wants to be the generation that has to juggle two systems in their heads all the time. If we switched today, my kids would grow up pretty much thinking in Metric and would have no problem. But I feel like I’d forever be doing that calculation in my head. Even if I knew 28° C was a nice warm summer day, I think I’d always be converting it back to 82° F just to make sure I knew exactly how warm it was, based on my past experiences. We don’t want to be the ones straddling the two worlds, dealing with parts in both sizes or wondering how to deal with machinery that still had Imperial components that were no longer allowed to be manufactured.

Besides, who has the guts to push an idea like this forward in the country today? If Republicans championed the cause, Democrats would rail against it. And vice versa. And unfortunately, engineers, scientists and the like don’t have the kind of lobby that would be needed to get politicians interested. Even a public relations disaster like losing the Mars Climate Orbiter (due to a conversion mishap) didn’t move the needle on fully switching to Metric. So I guess I’ll just wait with you for that long-off day when we get the first flying car—and wonder what kind of miles per gallon that thing will get.

62 Comments on “Why we won’t kill the Imperial System

  1. Interestingly, here in the UK we went metric in 1971 but many of us that were brought up using metric have adopted many imperial references from our elders. My 15 year old step son even uses a mixture metric and imperial. A total transition from imperial to metric would takes several generations as demonstrated here in the UK.

    • Late reply here, but I felt it worth mentioning that Australia certainly has not taken several generations for metric to be adopted in entirety. I suppose there may be a few old timers left who cling to imperial, but it hasn’t taken several generations to be successfully adopted.

      Metrification in Australia began around the same time as it did in the UK too.

  2. Um, its litres (liters) per 100 km and after 30+ years driving I still do not know really what that means but less is good. But aside from room temperature being around +72F and the freezing point of water at +32F I have to do a conversion every time I see temperature if degrees F. But I am pretty well 100% bilingual in the imperial and metric system when it comes to every day measurement but god help me if I have to do pressure in inches of mercury or inches of water or MPa or Decs. There I understand psi the best. And forget about slugs versus pounds versus newtons.


  3. You are correct, but if we do nothing, we will be in the same situation for several more generations. I am sure that some of our weakness in exporting our manufactured products is related to companies which have not converted to the metric system. Why don’t we start adding the metric equivalent on signage, gas station meters, bank thermometers, and etc. At least then we could make some progress, albeit slow?

  4. Many manufacturing companies based in the U.S.A. that exports and have clients that export use both systems. I have not seen any problems from this have you?

  5. Thomas Jefferson had conversion to metric as a primary objective of his presidency. He hated everything English so much that he wanted us to change. To bad he never succeeded.

  6. Some imperial numbers are more precise, giving them the edge in daily use.
    I don’t want to say “Is it 22° or 22.5°?” that half degree in Celcius is a big difference in Fahrenheit.
    Of course, the metric distances and weights are more precise than their Imperial counterparts, so it would more than even out.
    We, in the scientific world, could adapt. Can’t speak for people that need an iPhone to tell the time or calculate a tip.

  7. My college education was totally in metric and, thanks to federal AEC procurement rules, I am fairly comfortable working in metric professionally (is this a “hard metric” or a “soft metric” project?)(the fact that electrical design is essentially the same in both really helps).

    Driving, cooking and weather have me totally at a loss. Is $0.92/L a good price for gas? How many ml in a tsp? Sandy had a minimum pressure of nn kPa, how many inches of water is that (forget millibars)? I have a measuring cup marked in both units but not measuring spoons and no dual-unit or metric cookbooks.

    • $0,92/l (small letter :P) is a good price for gas. In central Europe we have ap. $2/l
      Atmospheric pressure is shown in hPa. You can tell, that 1000 hPa is 1Bar (average pressure on Earh), and it is also a pressure at 10meters below surface. Can you tell, how psi it would be at Marina Trench 6.831 miles deep? Cause in metric, you have 10911m, 1091 Bar :D

  8. Imperial screws are engineered for maximum strength per unit of mass. They break off heads about the same point they strip out. Metric screws are arbitrary and always strip out. They are always too heavy for their strength. But I prefer to calculate in metric because the units work out without conversion factors. Beware pseudo-metric! It needs conversion factors. Force is in Newtons, not kilograms or grams. They are mass.

  9. I had an the somewhat unique experience of completing my schooling whilst the UK changed both the money and the unit system and having to then go through Universiy in metric. Then I emigrated to the US in the early 90s after over 20 years of engineering work in the UK and was faced with relearning the so called British system in the US which ironically bears little resemblance to the Imperial system that I could only vaguely remember. So I am dismayed when people explain to me their percieved difficulties in changing to SI units. Just get on with it America.

  10. In reference to Robert’s comment, the millimeters are more accurate than inches. We usually use 3-decimal places in inch dimension. The .001 in is equal to 0.025 mm. What do we do then with the 0.01 mm? We round it off to zero in.
    I just wonder, what is the percentage of our import we lose due to, foe example, the imperial hardware the world does not want deal with when it comes to their replacement, etc.
    When I came to this country, it took me 15 minutes to get familiar with the imperial system and a few more days to get use to it. It really does not have to take generations for the conversion.

  11. @Bill Redmond – I’ll take gas at $0.92 / l – as much as you can give me…on this (metric) side of the pond, I paid $2.24 /l this morning…

    Getting over that, the company I work for has manufacturing operations globally, we design & deliver to both imperial & metric countries, our US site has transitioned from imperial to using metric where appropriate. The people didn’t really have a problem with it.

    There are other factors to consider though – e.g. maintaining a stock of imperial & metric fasteners for example. Also, common sizes of raw materials if a designer specifies 2″ bar, then that’s 50.8 mm, so any Ø50 mm barstock that you have won’t work. The simple solution would be to stock 2″ bar, but this leads to extra machining time for metric designs.

    There’s also a whole lot of gothas hidden in software, especially in-house software. If your inventory system is expecting feet and inches it’s not going to be happy with mm.


  12. It is very sad that just because of inertia, laziness, and stubbornness we stuck to Imperial System that is more complex for understanding and use than Metric one. Imperial System keeps us in previous centuries, isolates us from the rest of the world. We will not be able to effectively compete and collaborate with Europe, Asia, and the rest of the world without conversion to Metric System. Take all other countries who used to use imperial system as examples. They have overcome their inertia and converted to Metric. My 11 year old daughter is taught at school mainly metric units. So, she brings me hope that eventually Metric will prevail.

  13. Have you bought a Coke lately? People don’t seem to have a problem buying 1L or 2L bottles. My car has a 2.2L engine. We handle mixed units already – ounces, pints, quarts, gallons – and we do it by generally not converting. We just deal with the units presented. Adding in liters – or kilos, or cm – isn’t going to topple civilization.

    As for changing standards – I’m remodelling a house. Funny thing – a 2012 2×4 is NOT the same size as a 1956 2×4. Standards drift over time. (Or, as they say, constants aren’t, and variables won’t …)

    I think the change is going to come from the manufacturing sector – where use of metric is hidden. It’s already there in the auto industry and the aerospace industry; as other industries decide that it’s more profitable to work in metric, they will. The “public” cut-over will end up being a surface-level thing, and likely will be much less painful than people fear.

  14. Like a couple of other commentors, I am from the UK and I remember when we went “Metric”. The UK is still not completely metric, they have retained miles on road signs (Presumably for economic reasons), and they still sell beer in imperial pints (Presumably for sentimental reasons). Celsius and Fahrenheit were both used for weather forecasts on radio and TV for a while so people could get used to it. Nobody buys gasoline by the gallon in the USA, they will either fill the tank or buy a dollar amount. Looking at packaging, a lot of packages are not sized in round units – have you seen a pound tin of coffee lately?
    The reason the USA does not catch up with the rest of the world is just laziness.

  15. Weather temperatures are easy. 0 C is cold, 10 C is cool, 20 C is warm, 30 C is hot, in terms of wardrobe. Your summary was right on. Thanks!

  16. Let’s just make the transition, if for no other reason that I can then purchase the tools I want to use.

  17. We, in the colonies, actually tried, but ultimately failed, to convert to metric during the mid seventies. Our aging club pool, vintage 1976, is 25 meters, not yards, as is the case with more contemporary builds. The backlash was intense, however. The machinists in our shop complained bitterly, that “foreign” measurement systems were obsoleting their English-based tools. How did I know? The lead machinist told me so, after told him of the absurdity of metric kilometer posts being sawed to the ground on the Sammamish trail. He was not the least bit interested in the fact that I had logged all my training runs in metric, but boasted that he had gotten permission by the county for him, and his boy scouts, to cut them down, since “nobody understood them”.

  18. It appeared that most everyone in the USA played a hand in preventing the switch to metrics last time around. Those making the translations tended to round our numbers, but make the conversions ridiculously tight. On TV, weathermen proclaimed the current temperature to be 72ºF – 22.2ºC and the wind ranging between 8 – 15 MPH or 12.9 – 24.4 KPH. Engineers updated their drawing tolerances from ±0.001 inches to ±0.0254 mm. I saw many speed limit signs changed from 55 MPH to 88.5 KPK. Those communicating the metrics were either totally clueless or didn’t want the change to succeed. History has continually shown that those that control the media control the world.

  19. Think about it differently. Both systems work. Using this logic we should look forward to a single world language, a single world currency, & heaven forbid a single world religion…….. I don’t know about you folks, but for me, anything that hints at the creation of a plain vanilla society is a very bland thought.. What we should encourage is the desire to be different even in a global economy. If metric is our future, conversion to this system will slowly happen without intervention. I purchase the right bolts for whatever I’m repairing and never gave it a second thought until I stumbled upon this discussion. Enjoy the difference or assign it to the US legislature where it will likely die by a thousand cuts. ………….. Bob

  20. Back in the early 70s in the UK when I was at school the metric system was introduced. I did find it much easier to handle by comparison to the imperial system. In maths we used a mixture of both and I found that very confusing and so it came that I suffered through this change.
    For the past 34 years I have been living in Germany and I work as a design engineer. Now and then I am confronted with drawings and parts which have been produced using the imperial system. When it comes to converting fits to the metric system great care has to be taken to insure that the results are as they should be. Now and then I just have to take the risk of rounding up or down and until now this has worked out well. Luckily my CAD system can be easily switched to and fro or I can set it to show both dimension systems simultaneously.
    Interestingly most European countries also used the imperial system in the past. So it comes that plumbing pipes for example are still sold in imperial dimensions here in Germany.
    Anyone in Europe who buys a US vehicle learns quite quickly that they will need a second set of wrenches if they wish to toy around. Even here there have been a couple of interesting developments such as ring spanners which can take both systems.
    As one of my predecessors has already mentioned there is still a mixture in the UK and if we look deeper we will find that this mixture of systems can be found all over the world. Perhaps we should not forget, that people can adapt very well and most are not that concerned too much as long as they can achieve what they are doing.
    From experience I think if fair to say, that those who fight for or against the one system or the other mostly do it as a matter of principle and not really for technical reasons. Time will tell what the future will offer us but no matter which direction things go, we will survive.

  21. Just a couple odd comments, First the U.S. was one of the original 17 signatories to the “Treaty of the Meter” in 1875! Second, not all “metric” is “metric” for an example, Grab a Poclain fitting and compare it to a ” metric” fitting. Poclain fittings are “metric” in that they are dimensioned using mm but unlike standard they come in sizes like 17mm. Why? I’ve been told it’s becuase they are the metric equivalent to n obsolete British pipe size.

    Also what is the facination with BSPP threads? Not only are they dimensioned in Imperial units they use an archaic thread profile.

  22. In the mid 1990′s Northern Virginia tried and failed to convert the Civil Engineering firms to metric. Afterward I wrote an (unpublished) article as to why I believe they failed. here are two of my talking points in that article. First they wanted to use meters for feet and millimeters for inches. This may be fine for the Aerospace or Automotive engineer, but is impractical Civil Engineers. Here is a practical example. You are trying to dimension a pipe that has an 8″ diameter. That converts to 200mm. Using 200mm instead of 8″ is a 2.5 times increase in the number of digit characters required in the dimension string. Let’s look at another example. Here in Virginia our gutter pans are 2′ wide. that converts to 0.61M. Again the dimension string had to increase 2.5 times. This is a very real issue for the Civil Engineer trying to dimension his site or call out pipes in plan and profile. It is common practice in our profession to call out the pipe length, diameter, material and slope of a pipe on plans and in profiles. So the increase in digit characters is a metric killer. Look at the comparison below:
    6′ – 8″ RCP CL. III @ 1.25%
    0.61M – 200mm RCP CL. III @ 1.25%

    Would you look favorably on that kind of an increase in your profession. Especially if you, like us, had precious little room on your drawings? Keep in mind that we are constrained, by the counties to a sheet size of 24″ x 36″ [610mm x 914mm]. Also keep in my that we a site is measured in acres [hectares] not feet.

    Another issue with the metric system, AS THEY tried to implement it here, was that meters may not be the best replacement for feet, and millimeters not the best replacement for inches. Parctical example time. You have to do a site visit for bond reduction. When you are in the field pacing of linear distances of curb, or sidewalk, or pavement, or whatever, it is difficult to divide the number of feet you get by three, in order to come up with equivalent meters. A better unit of measure from that stand point would be the decimeter, which is almost exactly 4″. If the decimeter were used as a replacement for the foot, then you would multiply by three. Which is considerably easier to do in your head. On that same note the centimeter would be used in place of the inch. This also makes it easier when it comes to dimensioning your drawings.

    Please keep in mind too, ladies and gents, that Civil Engineers in the U.S. are already used to a decimal based measurement system. Also Amercians work more hours per year than many Europeans. So, before you say that we have no reason for switching over to metric other than inertia or laziness, there are practical reasons why we don’t switch. For one, we already have a decimal system in place and ready to use and for two, we work as hard or harder than others.

  23. All current measurement systems are arbitrary to some extend.

    The base 10 of the metric system was probably based on counting on 10 fingers. It’ll be obsolete when humans evolve to 12 or 8 fingers in both hands, or to 1 finger in only 1 hand (after millenia of clicking the single button of an universal remote control with one hand while having a robot attend to every need). The base 2 of the imperial system is more digital-compatible.

    The meter is based on the assumption that the circumference of the Earth at the equator is 40 000 km. It’s not only inaccurate but didn’t take plate tectonic theory into account.

    The definition of 100 deg C as the boiling point of water is accurate or not depending on atmospheric pressure.

    And the definition of 1 second based on dividing a day into 24 hours, then an hour into 60 minutes, then a minute into 60 seconds, is not only arbitrary but subjected to errors and variations.

    So the choice of either measurement systems is just as arbitrary as the choice of MS Windows vs Apple Os-X

  24. I find the inertia argument to be more the case than laziness. Just look at the comments.

    The metric system is slowly creeping into America, but at a snails pace. I think those educated after 1971, such as myself, have learned both systems. Granted, due to routine use, I can related to 68F more so than I can relate to 20C. But I think my generation and those younger are more likely to make a quicker transition. I think as the Baby Boomers move onto retirement you might see some increased momentum. No offense, but its the reality. Ask my Dad to change and I guarantee there is no foreigner going to make him give up miles, gallons or pounds for strange terms.

    As an mechanical engineer, I prefer the metric system for ease of use in calculations, but using fasteners and standard SAE (“Imperial”) specifications forces you back to non-metric. Much as the civil engineers who are pretty much stuck with default Imperial standards. I have to wonder how civil engineers in other parts of the world can survive using the metric system though? Different piping specifications? Maybe they use 0.6m and 0.2m to save a few characters.

    And modern American cars require two sets of wrenches? Actually the last time I worked on a Ford or Chrysler they were all metric already. I miss the Detroit transitional period where fasteners were a blend of metric and Imperial with no real rhyme or reason. Ironically, I had to torque the metric fasteners to foot-pounds.

  25. To Norman Dixon, I think 6′ is closer to 1.8M. How about use meters for everything? Then “M” can be omitted. In your example, the metric dimension comparison would be:
    2.032 RCP CL. III @ 1.25%

  26. I work in metric all day long. At Misumi all we deal with is metric machine components.
    I remember in the 5th grade(1970) that we were converting to the metric system. The speed limits were posted in both MPH and KPH. Gas stations were converting to liters. That was fun. My father got into an argument with the gas station attendant when his 20 gallon tank took 91 liters. I miss those days.
    We were on a good start but I think that we have back tracked. Maybe my kids will get it right!

  27. I have been in the construction trades for 30 years now and it always amazed me how people in these fields struggle with fractions when adding, subtracting or dividing them. At one point in my carrier I was working in a shipyard building Aluminum passenger ferries and the chosen unit of measure was millimeters. I was amazed at just how fast new workers would pick up on using it and more importantly tolerances were held to a consistent 1-2 mm where if the imperial system were used by the common laborer 1/8″ is considered good. So even though a total switch is not very practical in all cases using the metric system as a tool like this where the benefits are obvious then it becomes practical if not necessary to improve product quality and ease of use is saving time on each task where the educational experiences of the workforce may not be ideal. A tool is only good for what it is used.

  28. Wow, I’m Canadian, we pulled it off. That’s no comment about our intelligence, just an insinuation regarding a peoples adaptability and humility.

  29. I do my engineering projects in SI. If the input data are not in SI, I convert FIRST. If for some arcane reason the output is required in something not SI, then I convert LAST.

    I have been comfortable in metric since middle school in 1960 and my first set of end wrenches in 1966 was metric.

    Of course, I also am comfortable around other languages. I read specs for electrical components in English, Spanish, Italian, German, and French with little difficulty.

    I have moved on, someday we all will.

    And when someone gives weight in kg, I just think to myself, “kg on Earth.”

  30. It’s all just units.
    I agree it will take a long time to convert. Everyone knows what a 4 by 8 sheet of plywood is…a two by four, a 55 gallon drum, etc.
    I even noticed on home shows filmed in Canada…they use both measurement systems…and usually they lean towards imperial on building products.
    Funny thing about temperature….Farhenheit has more increments than Celecius from freezing to boiling point for water….but in the end…does it really matter?….they freeze and boil the same…..but….you go with what you are familiar with.

  31. Unfortunately, I agree that there are places where the Imperial system is easier to use, such as wood working and construction. A 1/8″ tolerance is usually good enough, but is that 3 mm? Would 4 mm be ok? For machining, using metal, I agree that the metric system is better because tolerances and measurements need to be much tighter, and now you are getting into 0.001″ or smaller. A similar comment can be made for ease of use for cooking. 1 tsp (5 mL) is easier to deal with. Is a heaping teaspoon 6 mL, 7mL, or what? The Metric system seems to have unts that are either too small or too big for easy everyday use. I am an engineer by trade, and use Metric all the time at work. Cooking or doing projects around the house, I use the Imperial system.

  32. Switching to the metric system was seriously introduced in the early 1070′s. It was sadly dismissed with an idiotic joke that we would starve to death because we wouldn’t be able to cook meals to a recipe (as if micro-waved instant meals weren’t already metric). The engineering community should have gone on strike until it was changed. The thought of a zero GDP would wake up any moronic Politian.
    Let’s get off our lazy butts and do it. I am certain that you and I would adapt quite quickly where it counts. Most of the things we refer to in everyday life are purely relative, and for those things that are specific, we already deal with them. I regularly (much more than once a day) convert values between the two systems, it isn’t fun, it isn’t hard, and I usually do it in my head.
    We have trouble competing in the world market because we have to have two sets of tooling. Yet, most everything you currently buy is made in a foreign country and it is already metric.

  33. Paul,

    I read your editorial on “Why we won’t kill the Imperial System”.

    Here are some issues:

    1) There IS NO so-called “Imperial System”. There are only a bunch of disconnected measurements like crowns, flagons, jills, jacks, barrels, furlongs, chains, etc. Example:
    I could design a fuel tank for liters, using metric length measurements in my head. A liter is 10 x 10 x 10 cm. You couldn’t do it for gallons or quarts without a bunch of conversions. There really is a “Metric System”
    2) Never, never, never “convert Imperial to Metric” or vice-versa. If the speed of light is 3 x 10E10 cm/s, why do you want to know how many miles per hour that is? Does it make you happier? Don’t waste a second trying to “make sense” of a measurement by converting. 20 degC is nice for a picnic. 37 degC is body temperature. 50 degC is too hot to touch. –30C is extremely cold. NEVER convert. NEVER use dual measurements.
    3) All of science is metric. So is the military, automotive, medicine.

    So your apologia for the Imperial “hodge-podge” is simply off base. I expected better.

    When I learn that the International Space Station is 1/2 Metric and 1/2 Imperial…I am embarrassed for my country. We continue to be not quite a first-world nation.

  34. There are some of us who have bitten the bullet and went metric (SI). You can read about it, starting on the front page of last Saturday’s (24 JAN 2012) Wall Street Journal. It seems we (USA) are going metric, millimeter by millimeter, while no one is noticing, watching the Imperial (or customary, or English) system of measurement fade into oblivion, not with a bang (as it should), but with a whimper. I just regret that I man not live long enough for its demise.

  35. Well, there are about a third of a billion of us now, so it’s gonna take some time.
    My metric anectodes…During my middle school years in the mid-70′s, due to military famliy relocations, I attended 6 differnt schools…at each one, by some stroke of misfortune, the science teacher would gleefully announce, “Today, we are going to begin studying the METRIC system.” I so hated the metric system, but thanks to repeitiion, I am ready if our conversion ever happens. (It seemed so certain an imminent at the time!) My favorite Metric learning aid at that time was a poster in my Freshman Earth Science class… Farrah Fawcett in bathing suit with her measurements called out as 100, 67, 100 instead of 36-24-36.. “Gee, Teach…you’re right, Science IS fun!”

  36. Paul,
    you cannot be serious about people not being able to switch to metric. Of all people, I would expect you and the younger generation to wholeheartedly accept metric. At least decimal fractions of an inch. A distnace of King’s nose to his extended finger has certain number of widths of King’s thumb? Give me a break. Quick, how much is 11/16 in decimal fractions? We missed the opportunity in early 70s to convert to decimal because of union pressures such that machinists would not have to buy new measuring tools.. End result? Lost mission to Mars where furlongs per fortnight^2 multiplied by slugs were not correctly translated to SI units consequently orbital injection burn was wrong.

  37. As an equipment engineer here in the states, we use imperial for our process modules, yet my major US robotics supplier is 100% metric. The tools work fine. I spend a lot of time in Europe so my ability to convert distance, weight, and money is fairly instinctual by now.

    As far as temps go, yes the Fahrenheit scale has more lines in it. But the clever mathematicians made something called the decimal place. Makes Celsius very easy to use as well as just as accurate.

    Despite being US born and raised, I prefer the metric system for all my design work. And no, I’ll never see it translate to general society.

  38. Us Brits seem to have managed quite well with using Metric as the “official” system while still using imperial for some things. Our road signs are in miles and speedometers in MPH people often refer to Miles per gallon but we buy fuel in litres. Generally I do stuff in metric but I also deal with BSP threads and 0.1″ Etc. lead pitches on components. Changing our road signs would cost a fortune for no real benefit so why bother. Luckily I have a functioning brain so this mix of metric/imperial doesn’t bother me. So anyway use Metric for engineering where it matters but don’t bother converting your pints of beer or road signs where it doesn’t really matter and having a brain that can happily work with both systems could be considered a benefit.

  39. @Kent McKesson

    Re. Piping in the UK we have 8mm, 10mm, 15mm and 22mm copper pipe (also various metric plastic pipes) but we also have BSP (imperial) for threaded pipework. Doesn’t seem to be an issue and changing BSP to a Metric system would be a nightmare due to all the adapters extra sets of dies that would be needed, so best to keep it as it is. There are adapters for copper pipe but that is much simpler than threaded pipe. We also have a mix of imperial and metric with Pneumatic fittings I’m currently making some 25mm dia 2mm pitch to 3/4″ BSPT adapters, such jobs are fairly normal for me.

  40. @John Kaufman A heaped teaspoon is a heaped teaspoon again we use teaspoons in the UK and I’ve never really considered how many mL it is or how many mL a heaped one is, it’s just a bit more than a non heaped one. Only an engineer would bring precision into cooking.
    Building bridges – precision matters
    Cooking dinner – precision doesn’t matter.

  41. It will be nice to have the same system that the rest of the world uses USA is problably the only country that is not metric.

  42. I’ve been involved in Architecture and Building for 50years, I grew up with “Imperial” and grew through to Metric. Not having to add fractions of an inch is wonderful. In Australia, builders/architects use millimetres only for measurement, surveyor use metres, clothes designers use centimetres, but at least it’s all METRIC. As for mishaps in conversion, I seem to remember a certain Mars lander that crashed because someone got feet and metres confused, and a large Airbus project screwed up due to Metric/Imperial misunderstandings. To all the feet draggers out there, get with it, progress, or retire.

  43. What a waste! When I learned about rulers and units at age five so as to build a boat, feet and inches were fine. Subsequently, elder siblings and teachers, mentors and professors took me thru the labyrinth of Imperials and Metrics to a degree in physics, and I was still OK with feet and inches. University physics profs even demanded that we learn the metric system, but it was not common in US labs during the 50s. The absurdity of our world was revealed though when my astronomy profs introduced me to light years, meters being inadequate for ethereal distances. I notice the media today uses light-years exclusively when referring to a stellar object.

    What I find most obnoxious are temperature units. I’ve been exposed to only six scales, but absolute zero came as a shock. Since it was figured out a century ago along with superconductivity, I find it curious that not a single erudite country has considered switching its population to the use of an absolute temperature scale. Our whole understanding of thermally modified processes such as electrical conductivity, the strength of materials, chemical reactions, and the weather – to name a few – would benefit if we used and worked with absolute thermal units.

    After working 40 years with screwball units, it occurred to me that our troubles arise not so much from our system of units, whether metric or Imperial, but from our number system. We have words for tens and hundreds, but not thousands. Then we have millions, billions etc. up to about 10 to the twentieth or so, but almost no one knows them beyond 10 to the ninth. But today’s life requires that we work with numbers over about about seventy magnitudes. Instead of devising a better number system, we stumble along with one descended from the Romans.

  44. There is a lot more to the “conversion” than a mere “fudge factor” between differently-scaled units. For example, the metric system of machine screw threads is not just a different mathematical scale factor. Many metric screws have impossibly fine threads, that strip if the metal is not hardened and fabricated to close clearances (I refer to these as having “threads painted on”). The colonists needed reliable fasteners that would not strip and jam despite their imperfections of manufacture. The thread pitch is specified as inverse inches, because it is easier to set up the gearing of a thread-cutting lathe (check this out: even European lathes with quick-change gearboxes cannot cut as many different thread pitches as a US designed lathe can cut inch threads). In addition, the head design of metric screws is crazy: slots impossibly thin so the driver twists, etc. High-quality metric screws made by US companies also suffer these maladies. It is a case of bad design, not manufacture.

    The argument for decimal is losing ground! Where is most number work done? Why, it is in computers, of course! What system does the computer use? Binary! There is no exact conversion between decimal and binary! Suddenly, the “carpenter system” (1/2, 1/4, 1/8 inches, etc.) looks better. I say this after fighting with CAD packages which generate numbers such as 1.4000000011673451 inches for the position of an object that I set under a 0.1 inch “grid snap”

    Why don’t we invent a binary-based unit system and advocate using that? We don’t for the same reason we don’t dump the inch system: tradition (and the fact that we have 10 fingers?)

    No matter what system we adopt, there will be advantages and disadvantages; it is a tradeoff. Better to keep things the same than adopt some new scheme that just had different disadvantages than what we have now. One of those things is tradition. That’s what “standards” is all about.

    We can’t even eliminate units that have direct linkage to metric, such as the carat!

    So before blindly advocating unit adoption, do your schoolwork and learn what the “metric system” and the “imperial system” really is!

  45. Not even the Europeans or the Japanese pulled it off! What is the thread on the bottom of your camera to mate to a tripod? 1/4 inch – 20 threads per inch. That if the camera/lens is too heavy for that? 5/16-18 or 3/8-16! Why? Because these proportions withstand mating/unmating the best.

    What is the size of the socket square drive in a socket set made anywhere? 1/4 or 5/16 or 3/8 or 1/2 inch. Even the Europeans (the “hard core” metric) use Imperial standards!

    Are you familiar with the Eurocard standard? It is a hodgepodge of mixed metric and inch units (different in the 2 dimensions of the board!) A most common board is 160 x 100mm with mounting hole centers spaced 1/4 inch from the edges! Check this out on Wiki.


  46. If the USA wants to be fully consistent, we Brits have another obsolete system you’ll just love – four farthings to the penny, twelve pennies to the shilling, two shillings to the florin, twenty shillings to the pound, two-and-a-half shillings to the half-crown, twenty-one shillings to the guinea. You can have it for free. Call it the New Dollar if you like.
    I was schooled in that nightmare, and inches, feet and yards,rods, poles and perches, chains, furlongs, ounces, Troy ounces, pounds and stones and hundredweights and tons and bushels and firkins… When I got to university to do engineering I happily forgot all that and went metric. Never regretted it. When the whole country went metric, there was a brief period of uncertainty, but now I never bother to think in Fahrenheit, for instance. And the relief when the currency went decimal…
    Two guilty admissions: I would resist buying my beer in the pub in half-litres, and I still do my carpentry in (decimal) inches. Sometimes the unit is just right.

  47. Those of us in technical fields already are familiar with and regularly use the metric system. And if your company sells internationally as most do these days, then you must use or at least be familiar with metric. Products that continue to use imperial hardware are at a disadvantage as the rest of the world has to have different tools to work with our products. As do we here when using metric products which most are these days. Yes, it will take one generation to convert and if we done it 50 yrs ago we wouldn’t be having this discussion today.

  48. It is far more complicated than that.
    Tooling and heavy fabrication equipment comes to mind.
    Most mechanics have both Imperial and Metric tools in their toolbox since both standards are used in local and imported items that are repairable.
    The manufacturing and fabrication industry that remains in this country is Imperial. Switching over requires changes to lathes, mills, shapers and other equipment whose foundation is based on gearing and threads (lead screws) that require replacement in most cases. It is not practical to convert them. CNC equipment may fare better with software based conversion.
    Mechanical designers have remained Imperial where US manufacturing was desired. American bolts and Imperial threads are well known and understood. We know 1/4 20 NC, 1/4 28 NF and 5/16 18 NC, 5/16 24 NF and 3/8 16 NC, 3/8 24 NF but do not think in M6 x 1.0, M8 x 1.25, M8 x 1.0, M10 x 1.5, M10 x 1.25, M10 x 1.0 yet Metric with its use of pitch results in fewer total pitches compared to threads-per-inch yet typically has not just coarse and fine, but in many bolt sizes Metric has Extra-Fine and Super-Fine pitches (e.g. M12 has 1.75, 1.5, 1.25 and 1.0 available).
    So the practicality of changing design thinking to Metric is more daunting in the world of things mechanical. There may be more design rules to be familiar with as well as knowledge of the intuitive choices (e.g. use of 8/24 NC seems rare outside of electrical boxes and finding them in hardware stores is more difficult).
    It IS encouraging to see that Ace Hardware is now carrying a broad line of Metric Hardware (Nuts, bolts, and washers in many types of heads as well as different strength grades).

  49. Being a 66 year old American, I grew up with “standard” units. Graduating with an AAS in Machine Design Technology in ’74, we had a minimal introduction to the metric system. “More trouble than it’s worth.” Over the years I have worked with both systems, of course. Most were “hard standard”. Some were “hard metric”.

    The only advantage I see of one over the other is cubic measure. Using metric has the advantage of very easy conversion from small amounts, ml’s, to large quantities, liters. And then, if we stay with cubic inches, there is no advantage until we get into very large quantities, barrels.

    The one aspect of the metric system that still irritates me is torque. Can ANYONE explain how to get one’s head wrapped around Newton/meters? What’s a Newton? Yes, I understand the acceleration due to gravity thing. However, I can’t pick up a 10 Newton piece of stuff and hang it on the end of a meter long bar, can I? If I could, would that produce 10 Newton/meters of torque? I can, however, pick up a 10 pound block of cast iron and hang it on the end of a 1 foot long bar. That would produce 10 ft/lbs of torque. Assuming infinitely light bars. Or is that lbs/ft? AND WHO CARES?

    Thank you for your indulgence in my rant.

    Back to the topic at hand; my opinion is that when it happens here, it will be just fine. Engineers will be happy. The general public will barely notice. The civil side will be a bit of a problem. As one of the previous posters illuded, what do we do with existing structures and the repair parts; 4×8 sheets of sheet goods, 2×4 lumber, etc. Gonna have to be a long time converting that.

    As an aside; does anyone know where the smaller pipe sizes came from?

  50. I’m pretty certain I carefully read the earlier posts but didn’t see any mention that the metric system has already won. For over a century the customary units here in the US have been defined by metric values ( T. C. Mendenhall, Superintendent of Standard Weights and Measures, Order of April 5, 1893, published as Appendix 6 to the Report for 1893 of the Coast and Geodetic Survey.) I was in high school when some of those definitions were refined in 1959.

    Example, an inch is defined as precisely 2.54 cm. So we’ve been using metric for longer than most of us have been alive and making the conversion in almost every measurement without ever knowing it. The biggest mistake our school system made was to drill students on the conversion between the two sets of units.

  51. Pingback: Ten reasons to hate metric units

  52. Living in Canada we get all 3 measurements to work with (British, American and Metric). I just love changing oil in the car. Do I get the 5 litre jug, the gallon (3.78L) or the gallon (4.5L) size. I don’t even know how to spell litre, liter anymore. My favorite part of our way is the overly accurized conversion we always see. For example it used to be about 100 yards to somewhere. Now it’s about 100m (109.361 yards), Part of my work involves collecting data from students. lots of them are 180cm tall and weigh about 180 pounds. When I buy plywood it’s still 4′x8′ sheets but for convenience we have it marked as 1220×2440. Not sure what happened to the other mm. I cut it into inches & carry it in the 5.5 foot bed of my pickup and top up with 80 litres of gas that’s going to give me 25 mpg, If i keep my 265/70-17 (that’s 265mm wide to fit a 17″ rim) tires filled to 300kPa or maybe 40PSi. I drive 50 miles to the next town at 90km/hr, where the wife gets me to pick up a pound of hamburger for $2/kg. She never tells me to ask for 454g, I use my 3/4″ wrench interchangeably with the 19mm one on 1/2″ and 12mm bolts. 10-32, 10-24. 1/2″13, 1/2 coarse and 16x2mm are all sizes of bolts and screws. Use the correct one for the application. The tough part is sorting out the nuts when the guy before put half 5/8 and 16mm bolts into a bunch of holes. They almost fit. I think it’s going to snow now, the barometer is down to 890mbar. Happy ranting guys, we should be at it for the foreseeable future.

  53. I don’t see any countries of the 95% of the world that use metric lining up to junk the metric/SI system in favor of the British Imperial System or the U.S. Customary System. How is it that they can successfully use the metric system and the UK, the U.S., and Canada, the only three countries in the world were Imperial/U.S. Customary weights and measures are legal and official, cannot? If the Imperial and U.S. Customary systems are so superior, more practical, more convenient, etc. to metric/SI, why are the Imperial and U.S. Customary systems not more widely adopted? 95% of the world can’t be wrong.

  54. It is so obvious: Metrics is the way to go – Once we start it will be easy. It is only a matter of days or weeks before we start thinking in metrics. Yes it is gonna be expensive but one day we gotta do it and let that be in 2014 !

  55. The writer states that if units were changed ” I feel like I’d forever be doing that calculation in my head”, but it’s in fact surprisingly fast how one gets use to new things albeit I admit it’s the easier the younger one is. My country changed it’s national currency to Euro some 10+ years ago and it took me (in my early-20′s) just about 2-3 years to “forget” the old currency, for my parents (late 40′s) a year or two more and for the last 5 years and in 6-7 years even my retired grandparent’s got comfortably used to Euro.

  56. Well. also the ” beggining of the metric system” is becouse of scientists and people argue about the way we dont need any logical stuff we just need it to function. The thing here though that is so weird is that the brain is logic whenever you want it to be. There is no such thing as ” im not a mathematican, Everyone is, you just need to learn it becouse all brains is logical and good at math,
    The way where its. Metric: 1 Mile is 10 Kilometers, 1 kilometer is 1000 Meters. 1 meter is 10 dm or 100cm
    1dm is 10cm and 1cm is 10 mm.
    Also the ” KM,M,DM,CM,MM is accually a acronym, its Kilo ” meters ” Kilo stands for 1000, Therefor Kilo (1000) Meters. See?
    Deci ( meters ) stands for 1 tenth, So 10dm is one meter.
    Centi is 1 hundreth 100cm is one meter.. etc.

    Me as a very mathematical person. I love math! have a very very ard time understanding how the impirial system is good in any way. Sure it was useful in the early times where we didnt have theese fancy rulers etc. you had to messure with your feet, thumbs, arms etc.. But why are we still using it now when we have a more precise and logical system, Becouse the imperial system isnt made to be an exact system, Just a quick system for anciant use.

    As some jerk said in another website that the us was a very technological country in the world and they used the imperial system and we others developed the metric system becouse we was too dumb to understand the imperial system is completely wrong. Its completely the opposite if you think of it. Also why do you think the scientists use the metric system?

    And with the Farenheit and celcius fights.. Like… I have tryed for sooo long to understand the logic in it but noo..
    Celsius. 0c is where water freezes. And 100c is where water boils.
    Farenheit: i dont even know—
    Kelwin: its a scientists system where 0 kelwin is the absolute zero. And then it goes up..

    Kelwin and celsius has a uniqe feature and has a ton of logic in it but common farenheit.. What are you doing?

  57. The eternal question and until the gouvernment does take a stance. I grew up with metric units and despite working with customary units for almost 20 years, it’s still much more cumbersome to do the latter. It’s totally fine to remain on customary units if all you want to do is stay within a limited area or field. Heck, I am building my deck in inches because all the materials are in customary units (as senseless as it is to use a 2″x4″ which is actually 1.5″x3.5″).

    However, it’s a global truth that metric is THE widely used standard and arguing about cost or effort it takes to convert simply delays the inevitable and increase cost and effort further … unless the US want to stop importing and exporting.

  58. Pingback: The intelligence of the Metric System

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