I challenge you all to make two changes today with regard to this. First, switch your phone to give you the weather in Celsius. It gets super simple fast:
0 and below - Freezing. Wear a warm jacket and closed toe shoes or boots.
1 - 10 - Cold. Wear an overcoat (a light one if you are used to colder weather)
10-15 - Early spring time. Long sleeves are probably in order, maybe even a sweater.
15-20 - Late spring. Wear short sleeves.
20+ - Warm to hot. Wear short sleeves. If it gets to be 24+ shorts are appropriate.
I am deliberately not giving conversions to Fahrenheit here because I think that's how you just go back to using it. Try to internalize the metric system here.
The second challenge is to switch your clocks/watches to the 24 hour mode. Not strictly metric system related, but you will not have to worry about AM vs PM again.
For the advanced users: switch your car to show your speed in km/h instead of m/h.
For the super-advanced users: try to figure out how many liters per 100 km does your car consume :).
Edit: if you cook (and you really should), use a scale set to grams instead of measuring cups for any recipes you are making. Almost all foods list both oz's and grams on them. You will get much more accurate measurements this way and will learn to gauge what 150 grams of cheese looks like, etc.
Specifically regarding temperature, I don't think Celsius is granular enough, unless you like working with fractions. For instance, in my home, I can feel the difference between 72 F (22.2 C) and 73 F (22.8 C), and I prefer 73 F. Fractions would be just as easy for me to decipher, but there are some dim folks out there that have to be catered to, because they are legitimate consumers.
Regarding other measurements, I agree that metric should be used, because it just makes sense. Millimeters are about as granular as 1/16 inches, so that would eliminate the need to work with fractions in most cases.
> I am deliberately not giving conversions to Fahrenheit
But I spent all that effort learning what temperature water boils at in Fahrenheit. Who the hell is going to remember what that temperature is in Celsius??
Does most of this apply to newer things (cars, clocks)? My car has a clock but I have no method of changing anything but the hour/min. The speedometer is analog...I guess I could try to read the small print that displays in km...my alarm clock doesn't even have options for 24h.
With the cooking one (assuming you meant recipes from books); all the cookbooks I've seen have nothing in metric so I have to do another step of converting before I can measure properly.
The only problem I have with taking up your challenge is...why? I'd be the only one of the people I know and I would have to convert everything for them when I communicate.
If everything tomorrow and beyond was in metric, I am guessing a lot of people wouldn't replace their old items with the new one (displaying metric) they would just find a quick way to convert from their current way.
I have a car imported from US here in the EU and while driving it I just look at the smaller print in km/h, I honestly don't even notice the larger letters in miles now, it just became natural to look at the smaller print.
It still doesn't make much sense here though. I assume that where you are the speed limit is in km/h. Here it's mph. No matter what I have to know how fast I am going in mph so it makes no sense to bother knowing what I'm doing in km/h. If they changed all the signs to km based speeds (overnight) then I would probably do it but more likely I would remember where on the mph gauge the common km speeds and use those anyways.
Yeah, it sounds likely - but my point is that you would get used to it after a few days,and could continue using your car exactly as you did before. And all new cars would be produced with dials using km/h as the main unit,so the problem would eventually go away on its own. The only problem that I can think of occurs if your car somehow doesn't have a dual kph/mph dial,and shows miles per hour only. Then yes, it becomes an issue.
You do know that Fahrenheit was designed with humans in mind, while Celsius was designed with water in mind. The average person really doesn't care at what point water boils or freezes. They care about hot and cold, something F does better for humans than C.
Actually, this is a great point. As someone born and lived almost all my life outside the US, I just couldn't understand the Fahrenheit system. Having spent the last few months in the US, I went the opposite way to try and force myself to understand Fahrenheit and what I found was very surprising.
Fahrenheit actually makes sense if you consider it from a weather perspective. The only way to use the Fahrenheit scale is to look at it as percentage of body temperature. Now, I know that the body temperature isn't 100 but 98.4. If you keep that part aside for a minute, it's very easy to explain the Fahrenheit scale. 50 degrees is 50% of your body temperature. 32 degrees is 32% of your body temperature. 100 degrees means that weather is equal to your body temperature. That means things like if the weather is hot or cold is just percent of body temperature. Also, 0 degrees is the temperature at which brine freezes. So, no matter how much salt you add, ice will not melt.
Historically, when the Fahrenheit scale was invented, body temperature was supposed to be at 100. It was later realized that the body temperature is slightly less but no correction to the scale was made.
Every other scale makes no sense to me. I convert pounds to kgs, miles to kms, gallons to litres etc.. all the time just to get a sense of measure. But for the weather, Fahrenheit is really good.
It reminds me when we moved from national money (Franc) to Euro in Europe. The conversion rate was something like 1 Euro was 1.67 Francs (IIRC). I don't remember how long it took for the shops to remove the dual price tags, and when people stopped using converters or doing the conversion in their head. I decided just to forget about Francs from day one of Euro.
It would make a lot more sense if we used a system where 0 was the coldest it normally got, and 100 was the highest it normally got. Way more integer data points, and a lot less use of negative numbers.
I was joking, Fahrenheit is basically setting zero to the lowest temperature most people run into outside, and 100 to the highest temperature run into outside, in Europe.
So Spain's not part of Europe? They push up over 100°F there on a fairly regular basis.
0 through 100 is really just a part-time thing at best.
In °C the same thing plays out as somewhere between -40°C and 40°C where at the bottom of the scale it's really cold and at the top it's really hot.
Plus it follows the simple rule of "negative numbers mean ice outside" which is important from so many perspectives. That makes a lot more intuitive sense than "numbers under 32".
I find the inches and feet to be easier to use than said pound and stone .... Not to forget those silly cooking measures like cup, bowl, tea spoon etc... which obviously are not standardized. Talking about weird measure, is the fact that properties seems to be advertised in number of rooms and not square meters or square feet.
The strange thing about articles like this is that they seem to assume that converting between units is something that happens all the time, such that doing so is a huge drain on the economy and engineering time. I don't know if my experience is the common one - but with a few exceptions (inches/feet, oz/pounds) such conversions seem kind of rare. Instead, you pick an appropriately sized unit to begin with, and stick with it.
It's interesting to note that all of the examples the article gives are caused by metrication - which forces conversions - rather than by problems using the customary units.
I don't see the point of a half-assed metrication, where everything remains the same size but is measured in centimeters. (Such that lumber is sold in lengths of 243.82 cm rather than 8 feet.) The US is already half-assed metric in a lot of places, with both customary and metric units printed on packaging when appropriate.
I guess the question is - what are the benefits of metrication that justify the massive expense required to convert?
Probably a host of stuff from one less NASA orbiter crashing, down to not having the sticker on millions of car B pillars printed with imperial and metric tyre pressures.
There are lots of downsides, it's interesting you give a construction example; in the UK we have houses built from imperial bricks. Metric bricks aren't the same size, but a conveniently round number in millimetres. A house I'm buying was built in imperial bricks and someone with not quite enough sense has filled in some old doorways with metric bricks.
The costs of maintaining different systems aren't large but accumulate indefinitely, the cost to switch is finite.
Again, it's interesting that all of those are issues caused by metrication, the switch to metric units, rather than issue caused by customary or imperial units themselves.
> The costs of maintaining different systems aren't large but accumulate indefinitely, the cost to switch is finite.
That only makes sense if there's no discount rate, nothing else that could be done with the money we'd spend to switch. I suspect there are a lot of things that could be done that would yield higher rewards.
> (Such that lumber is sold in lengths of 243.82 cm rather than 8 feet.)
It's interesting that you pick that example. In many cases, the "measurements" for lumber don't actually correspond to the true dimensions of the product purchased. For example, a "2x4" has dimensions of 1 1⁄2 inches x 3 1⁄2 inches[0], rather than 2 inches by 4 inches. So, at least for the example you give, it's not clear to me that converting to metric is a bad idea, since the specifications are already somewhat nonsensical. Granted, a "2x4" does have a standard size.
Having worked in construction, I think it is the last point you make that is most important. Though a 2x4 is 1.5x3.5, it is a standard dimension. In the US, construction standards (lumber sizes, door frame sizes, ceiling heights, etc) are all in feet and inches. Changing them creates a compatibility nightmare. That said, I don't know of other industries that suffer the same challenge (perhaps others can think of them). Bicycles for examples transitioned reasonably quickly from English standards (e.g. 1 in. stems and 27 in. wheels) to fully metric for road bikes at least.
It is not nonsensical, 2x4 is the rough sawn size.
Edit: Since I can't reply because of HN's helpful 'You're submitting too fast' notice, I will reply here. You can still buy rough sawn for working on existing structures and for aesthetics when exposed.
I don't have primary source info, but from the wiki article I linked, that used to be the case, but is no longer the case. All that matters now is the final cut dimensions.
I am not sure if this fully answers your questions, but one of the places where unit conversions happens a lot when doing customary unit engineering calculations is dealing with various constants/properties. For example, you might get the specific heat capacity of some material in terms of gallons, but you're dealing with ounces of fluid, and so you stick a conversion in there. It's certainly kind of niche, but it's really annoying to deal with.
But agreed on the half-assed metrification. I'm from Canada. I still buy pop and beer in 355ml cans, 591ml coke bottles, 600ml pepsi bottles, and 2L big bottles. My wood is still sized in inches (or nominal inches).
(I fully support SI though. In theory, I no longer need to memorize a whole set of conversion constants. In practice, I live in Canada, so I still need them).
Because I don't want to look at 243.82cm on my tape measure, or if I am trying to lay something out to match the 16 in on center studs 40.64 cm, 81.82, 121.92, 162.56, 203.2, and then 243.82 cm.
For new stuff you could probably cheat and just base it on 40cm, which would be fine and perfectly acceptable, but for the old stuff which is still out there over the 8 feet, I'm already off by more than an inch which is enough to not hit the stud. Most framing isn't great, but still the error is additive and fractions are hard enough to work with that I'd want to avoid it.
I think the transition for lots of things really has an additional cost. Is that speed limit sign metric or imperial? Sometimes its obvious, other times not, and there are thousands and thousands of different governments responsible for them.
The point is that the US would be half-assed metric whether it wanted it or not because it's part of the global economy. So your choices are half-assed metric or full on metric. There are no other choices.
These articles are always missing the subtly of the issue. I'm going to ignore MPH signs & mile markers, because they really don't matter much for international interoperability. The important things are focused around dimensions on parts, packaging, engineering drawings, etc.
Sure, we all know that lots of areas in the US already use the metric system. I have personally used metric in the biomedical & consumer electronic industries, but had to use imperial in the defense industry. Generally the more advanced or international the industry the more metric it is. (That's why construction may simply never switch).
What people generally don't realize is that other countries are still using the imperial system because the US drives the market. Lots of imperial system parts are made in Mexico, China, etc to feed into US supply chains. Complete wild ass guess, but I bet more imperial system bolts are made in China than in the US.
It's not like there is a ban on making non-metric parts in the 'metric countries'. They'll do it, and often times non-metric parts are cheaper even coming from metric countries because of the volumes.
It really seems like an industry by industry fight, and by and large it is a ratchet turning in only one direction. Even the defense industry is started to use metric for some parts. I think 50 years from now it will be a moot point.
your comment about having to use imperial in defense industry reminded me of working for the US Navy in the early 90s, where a standard unit of measure is a "kiloyard" (1000 yards) when measuring the range of sonars. Apparently a lot of the early testing had been done using yards as a unit. Since people often round to the nearest whole unit, they thought converting those historical measures to meters would introduce inaccuracy, so they continue to measure in yards, which yields big numbers with modern gear. Rather than use miles (1760 yards) as the ranges got long, they use kiloyards to record all data (presumably because dividing by 1000 is easier than dividing by 1760). Only in America...
What's your point? I also try to only use metric in the us, and a m3 Tap and bolts is cheaper than whatever silly fraction equivalent even buying from.consumer stores here. So, yeah, the economics of all this is crazy.. But i think the point is to improve it even more by removing the odd ones entirely.
That if the only country on earth making things in imperial was the US, there would be a greater economic incentive for the US to switch. Since that is not the case, and many countries are producing imperial parts, a lot of the supposed benefits of switching listed in all of these articles are simply not real. If there really were high costs imposed by sticking with the imperial system, someone would be making a business case for switching over to metric as much as possible. As far as I can tell, outside of labeling and government procurement, nothing actually forces American companies to use imperial, other than their own internal cost/benefit analysis.
It's hard to "make people think" in the different unit system. I'm in the UK and people talk about sizes in feet and miles all the time even though the society is supposed to have switched to the metric system.
There are places like on product labels where both units should be mandatory. Hopefully in a few generations people will gradually switch over.
> It's hard to "make people think" in the different unit system
It is, but it can be done in just one generation. The generation that is raised metric finds it even harder to think in imperial measurements, since the imperial measuring system is significantly more complex. Source: I grew up in a fully metric country.
I just looked it up, apparently the conversion to metric happened around the time that I was born. I had no idea, I thought that it was a decade or two before that.
i.e. if the USA had tried a bit harder in 1975, they would be done now.
Also, the UK is not "fully metric". If it was, there would not be road signs showing numbers in miles and miles per hour. You can't stop people from buying beer by the 568ml, but if the UK was serious about metric, official communications and education would be all in metric.
Something that is often overlooked: in the EU a dozen countries switched to a different currency overnight. Everything. Accounting and banking, shops big and small, the entire value system was redone.
But after more than a decade I still find myself converting back to the old currency in my head from time to time. Only to remind myself that inflation has made that exercise pointless. The older generation has trouble with it, though.
We here in Ireland were the same in that regard. A few years ago, we just decided to abandon the use of dual units and switch to using km everywhere. Within a short amount of time, people had mostly switched over to using km for any non-trivial distances.
It can be done; it just takes the determination to just do it.
As a USian I can testify that there's a lot of irrational opposition here. Disclaimer: I don't have scientific sources on this, just subjective impressions from a lot of little interactions and clues.
The resistance seems to be largely: (a) older people who doubt their own ability to adjust (b) right-wingers who are convinced it's a socialist conspiracy or somesuch (these are people who think international cooperation is taking sovereignty from the US, or something like that - they're a bit incoherent) and (c) politicians perceive it as unpopular and risky to advocate (presumably because of a and b) or just not a vote-getter.
I've occasionally tried to promote SI by using units in casual contexts, but it's perceived as pretentious or obnoxious. The situation is better online as I participate only in fora like this where US obtuseness is not necessarily expected. It is hard to even find products like thermometers and measuring cups (for cooking) with all-SI.
In the European Union we changed currency, which is arguably a riskier change of measure, and much more abrupt a change.
We did fine! Even my grandma got accustomed quickly. Of course one could argue that is precisely because of the importance of a currency that we adapted so quickly...
Yes, it's difficult to make people think about it. At the same time, sometimes the units "don't matter" (like speed limits, 50 is 50 in the speedometer, just make sure you're not looking at the mph scale)
I want to slap somebody when I hear about "pounds" or "feet/sq ft", or even worse, Fahrenheit (since this is a non-linear transform)
At least everything in the supermarket is marked per pound and kilo
" Admittedly, I'm not entirely sure why being a non-linear transform gets the OP so riled up."
Because it's harder to calculate mentally
One can approximate 2lb to 1kg roughly, 1mi ~ 1.6km, but for Fahrenheit this is harder
One solution is to establish a set point ( 70F = 21.1C, approximate to 20C ) then work in differences, since 1.8deltaF = 1deltaC so, 2dF ~ 1dC (or 10dF ~ 5dC)
Hence, 90F is approximately 30C (exact value, 32.2C)
In engineering, linearity refers to having two properties:
a) f(x+y) = f(x) + f(y) where x, y, are two values, and f is a linear transform/function
b) af(x) = f(ax) where a is constant
In this case, the transform is the conversion between C and F. Since there is +/32 in there depending on direction, neither of these properties hold.
For example, yards to meters is a linear transform. 3 yards converted to meters + 2 yards converted to meters = 5 yards converted to meters. This is not true of temperature. Adding 32F to 32F gives 64F, which is not the same as adding 0C to 0C.
I disagree. When I'm working with computers, I find 24-hour time more convenient. It was a little difficult for the first few months, but now I really am ready to think only in 24-hour time.
Unfortunately, my brain won't fully switch over because everything else in my life is 12-hour time. Having both means I can't help but stick to the old way. When my computer clock says 17, I know people will start leaving the office. But, when it says 19, I don't think of supper. Supper is when my kitchen clock says 7.
Having a short adjustment period would be good, but at some point you just have to commit. Generations is too long in my opinion.
Are people thinking that a 24 hour time is metric? I saw a couple of comments that make me think this.
In Australia we use 12 hour am/pm almost all the time, even on official documents. We've been metric since the early 70's. I still have to pause and convert when I see a time greater than 12 (or, sadly, less than 1.)
It seems much more a cultural thing, that one.
Now if we could only stop anybody using m/d/y date formats...
I think most people in the UK use a pretty mixed up set of measures.
I think of beer in pints, wine in ml, driving distance in miles, walking distance in km, height in feet and inches, but weight in kg. Lengths are in m/cm/mm as are weights and volumes for cooking. Mountains in Scotland in feet and mountains in the Alps in metres...
Oddly, my teenage son uses m/cm for height and stones/pounds for weight...
> I think most people in the UK use a pretty mixed up set of measures.
I agree. But for science and engineering (where metric is really useful), I believe that everything is metric here now.
The measures for which we still use Imperial units are ones that generally are just directly and subjectively compared by humans, rather than any real engineering work.
Another way of making my claim is that nobody really has to input Imperial measures into a calculator any more, or make any conversions [involving non-metric units] for engineering purposes.
I suppose there are some exceptions (eg. BMI), but these calculations are generally isolated and have no wider unit-incompatibility impact.
A bank officer recently heard the following explanation for a farmer's financial trouble:
It all started back in 1966 when they changed from pounds to dollars. My bloody overdraft doubled.
Then they brought in kilograms instead of pounds, my bloody wool clip dropped by half.
Then they changed rain to millimetres and we haven't had an inch of rain since.
They bring in celsius and it never gets over 40 degrees. No wonder my bloody wheat won't grow.
Then they change acres to hectares and I end up with half the bloody land I had.
By this time I'd had it and decided to sell out. I just get the place in the agent's hands when they changed from miles to kilometres. Now I'm too bloody far out of town for anyone to buy the bloody place.
I would like to see the USA switch to the metric system. However, I will point out, just because a "new" (the metric system was developed during the French Revolution) measuring system is more rational, does not mean that it will catch on. I'll offer a hypothetical example of another change that would be rational:
We currently divide the day based on time a system of time developed by the Babylonians roughly 4,000 years ago. Because the Babylonians had a math system that was base-60, it was rational for them to divide the day into sections that fit easily into a base-60 system. Ideally, they would have been consistent and gone with 60/60/60, but for some reason they went with 24/60/60. We have 24 hours, then 60 minutes, then 60 seconds. There are 86,400 seconds in the day, which may have made sense to them, but it makes no sense to us, in the modern world, since nowadays the whole world uses base-10 math. If we wanted to modernize the time system, we would switch to a base-10 system: 10/10/10/10. That would mean our smallest unit of measure would be a 100,000th of day, which would certainly be easier to work with, and reason about, than the crazy 86,400ths we have to deal with. 86,400ths are an artifact from the dawn of civilization, and should be gotten rid of.
Will we ever have a clean and rational 10/10/10/10 system for dividing up the day? Probably not. From the Babylonians we get the 24 hour day, the 7 day week, and the crazy idea that a circle should be divided by 360 degrees. All of these ideas are so deeply embedded in our culture it would be extremely hard to change them. Clean and rational systems do not always win out.
I keep hoping that the USA will switch to the metric system. On that front, I still have some hope. On other fronts, such as a rational system for dividing the day, I have no real hope at all.
Metric measurements just make sense. I never understood why the US does not adapt and use this system. I was glad my engineering education used it, so that once again, I felt back at home using the metric system. Ask any US born engineer and they will likely tell you that if they had been using the metric system all their lives, they wouldn't have had to waste all that time trying to learn it in college for physics, etc..
The US already uses the metric system. It is taught to every child in school. Engineers and scientists use it as their default.
What the soi-disant pro-metric faction really wants is to stamp out the English system from the culture. Why can't they tolerate people measuring themselves, their recipes, their temperatures, and their vehicle speeds in their preferred units?
I think there has already been significant discussion here about what the advantages (and disadvantages) are.
The US rarely uses metric in it's popular culture. Weather reports are in Fahrenheit, movies almost always use miles and pounds. By any measure of cultural output that you export that I've seen (and Australia is a huge consumer of your popular culture) you do not use metric.
I've heard the argument that the US already uses the metric system before by people who are resistant to the US using the metric system. It always sounds disingenuous.
But I may be wrong. I have not walked one point six one kilometres in your shoes.
I don't see any mention at all here that the United States adopted the metric system officially as legal for all purposes in 1866.[1] Because this was by act of Congress, the Supremacy Clause in the Constitution means that all state governments have to fall in line and permit the use of metric measurements--and they do. It is custom alone that has slowed the thoroughgoing adoption of the metric system in the United States. Lots of subsets of private industry have been mostly metric for many years,[2] so we are talking about activities at the margin of international trade and science and other activities in the United States that have long been increasingly metric.
I have lived in Taiwan for six years of my adult life (two three-year stays) and I have become used to thinking metric about overland distances in kilometers or my own height in centimeters or temperatures in Celsius degrees. But over there too, customary units survive long after official metrification, although some of those (like the unit of weight 斤, usually translated into English as "catty") have been conformed to the metric system by being defined in metric units (so that now a catty is half a kilogram). This process may go on for a long time in the United States.
Hearing Fahrenheit in Toronto does surprise me on the few occasions that it happens (usually either retirement-age seniors or American visitors).
Recently I noticed the medical profession has come on board with cm/kilos for measurement which is pretty surprising since hearing inches/pounds is still fairly common.
Having grown up in the 70s and 80s I still find I float between the two fairly easily but I sure did find Scotland confusing last time I visited - as a metric country they sure do a lot of things non-metricy.
Scotland (as part of Britain) is not metric as far as I know. The imperial measurement system was created by the British after all. The rest of the EU is metric, but not Britain.
We (Scotland / UK) are metric for almost everything - science/engineering, medicine, quantities of food etc.
There are a few exceptions in more human measurements - beer is measured in pints, burgers and steaks in ounces, distances on roads in miles and personal dimensions in feet and inches, barleycorns and stones.
Britain, including Scotland, is Metric. The fact that metrication happened in the 60s means people of a certain age describe the weather in both F or C, depending on the situation.
The UK is certainly unique in the EU for its exceptions which include the use of miles per hour for speeds, miles for distances and, for example, 'pints' for beer. But much EU legislation on the sale of goods has been enshrined in UK law and means that most items have to be sold in metric units of weight/volume etc.
> The UK is certainly unique in the EU for its exceptions which include the use of miles per hour for speeds, miles for distances and, for example, 'pints' for beer.
Given that all official road signs for distances and speed limits in Britain are still in miles, I can't accept that it is a metric country.
I wonder if a successful TTIP agreement would be the catalyst for this? It's inexplicable that the EU/ EEA would allow for non-metric goods to freely flow into the market.
Should it also be illegal for the UK to teach Imperial units? I find the European attitude that government should ban everything they don't like perplexing.
In the EU, when we had to change from national currencies to Euro, the outcry was big -- because everybody was only able to "measure" money in the old currency. That even exactly this currency changed over the past decades very much, seemed to be not in the minds.
I guess, there are still people out there, which recalculate into Francs or Marks, or whatsoever -- but I think most Europeans have adapted.
So, when "old Europe" can change -- why not "modern USA"?
The article doesn't go far enough in showing the genius of the SI system (known as metric system most of the time).
The conversion factor between mechanical values in the SI system is 1.
Example:
E = F * delta_x
= m_1 * a * delta_x
= 0.5 * m_2 * v^2
Energy = 1 J
= 1 kg * m^2/s^2
= 1 N * 1 m // Force: 1 Newton applied for 1 meter distance
= 1 kg * 1 m/s^2 * 1 m // Acceleration: 1 kg accelerated at 1 m/s for a distance of 1 m
= 0.5 * 2 kg * (1 m/s)^2 // Velocity: 2 kg accelerated from stand still to 1 m/s velocity
So you can see that no magic factors popped up at any point. This is because the SI system describes the real world very well: for example mass and force are rigorously defined units and can not be used interchangeably.
While you are at can you change the date format as well? DD/MM/YYYY instead of MM/DD/YYYY (US). It should go from small to big. The other way around makes my head hurts every time.
The best part of YYYY-MM-DD is that almost nobody uses it, so it'll be easier to get everybody to support. I don't think we can standardize in either DD-MM-YYYY or MM-DD-YYYY.
There is a link in the article to metric interstate highway of Arizona. I-19 from Tucson to Nogales is signed in metric. When you enter the freeway there is a sign that says "This highway signed in metric" Every sign on the freeway is in metric, EXCEPT for the speed limit sign. I realize they did that so people wouldn't be doing 100+ MPH but I always wanted to drive it at 60KPH, and explain to the judge "the sign was in metric"
Some thoughts on a conversion that I don't generally see brought up:
* From an economic standpoint, the US is a big enough market that it is profitable to make things in weird US units, you have 350M people to sell to, most of whom are pretty well off by world standards. It makes sense to make a line catering to them. If businesses can start making a true or good economic argument it will happen more.
* Tooling that exists in standard units seems to be a bit of a red herring: I dislike having to own wrenches in both standard and metric units - a transition to one set would actually be nice. At a larger scale, i.e. manufacturing, it would make sense to start replacing things with metric on regular maintenance cycles. With very long cycle things just having a label change.
* Paper would be a nightmare for a while - A4 and 8.5x11 are just dissimilar enough for it to be weird, and paper has a very long lifetime, dual storage systems are a pain.
* A lot of very low level infrastructure has built in assumptions about standard measure that would take a long time to convert, and some would never convert. For example, a lot of cities put roads so that $X blocks is a mile. The midwest from the air looks like a quilt - thats because all the fields are partitioned by roads which are (generally speaking) a mile apart. Land ownership for rural areas is by the fraction of a section, and by acres - it's built in to how everything is laid out. These aren't impediments but it does create a weirdness. I navigate the backroads and a lot of parts of cities by knowing how far it is and just counting how far over and how far up i need to go subconsciously, and it is an issue.
* Now is a better time than ever for doing this in terms of accessibility to the public. Everyone has a smartphone - apps to do conversion in lots of intuitive ways can ease people's discomfort.
* Car, motorcycle and other mechanical equipment manufacturers should be the people to start the transition. They can all agree to just stop using standard things for the 20XX line of equipment. Or be legislated to do so. Similarly gas stations can be required to change on $DATE, and car manufacturers can just send everyone stickers to put near the gas-hole of cars to say "your tank is $X litres". I think this would help tons. No dual labeling, just bam - it's in litres now.
* Housing things are another weird infrastructure thing: they last for a very long time. Codes are all in inches -- doors must be 36" wide, switches must be placed at 48" and so on. The sudden appearance of a second width and height for new stuff would be bizarre, or building it at 91.44 and 121.92 cm respectively would also be annoying.
I still think it's a good idea, but some thought needs to go into these weird cases that are surprisingly common before a transition would be acceptable. But like I said - everyone carries a computer or two these days, so there is probably a lot of work that could be done to simplify the transition via good apps.
To be honest, the U.S. really should have switched during the late 19thor very early 20th century before the benefits of the industrial revolution gave us so much stuff that needs to be converted. Even if we converted tomorrow, we'd still be dragging around imperial measures for decades, maybe a century.
I can't see cooking or property measurements making the transition within my grandchildren's lifetimes. In most countries that have metricized, property remains a very stubborn holdout.
Commercial products could convert much quicker, it's mostly a label change during the next minor packaging refresh, followed by the next major packaging refresh adjusting the size to make the unit look better. (1lb -> 453.592g -> 450g)
Paper might take decades, companies have significant investments into handling standard paper sizes, from production to clipboards to file rooms. Going paperless is probably more likely. My local mechanic is now almost entirely paperless for example, but the final bill is still printed out on 8.5x11 paper and a copy filed away.
I agree that manufactured goods should just set a date and switch on the next model year. Eventually the older imperial items will just rust away, with a few examples kept alive by very dedicated hobbyists.
But some niche craftsman fields will probably never switch. Printers still use points and picas despite trying to metricize for a long while. You end up with incredibly awkward metric units for these things when you try to convert, and lots of the handiness of customary units (easy fractional divisibility) comes into play.
Basically is a mass unit (in Brazil and Portugal), originated at the imperial system (with an arabic name ar-arub meaning "the fourth part") of 25 pounds. The times changed, but it is still used in our metricized society for livestock weight. But adapted to a rounded number in kilos, nowadays 1 Arroba = 1 kilogram.
Well, there were other arbitrary changes along the way. I think the wikipedia article deals with it. By the time someone changed it to kg, wasn't even 25lbs anymore. Who knows who decided it would be 15kg - but that is kind the point of the oddities when change measurement systems.
> I dislike having to own wrenches in both standard and metric units
I think you mean "I dislike having US customary and standard metric units".
When it comes down to it, everybody else in the world managed to buckle down and just switch to standard metric units and ISO/DIN paper sizes. There is nothing special about the US that makes it any more of an imposition for them to switch over. Many of the issues you've outlines are the same as ones that countries like the UK, Canada, and Ireland have had to deal with when switching over to metric everywhere, and we somehow managed it!
In some sense, the metric system was a blessing, as it was foreign to all countries. Countries would never have switched to, say, the German standard of measurements (counterpoint: they did just that for paper sizes)
We here in Ireland decided to move away from dual use of units (miles and km) to just km a few years back. Sure, we're not a big country, but we also have more road per capita than anywhere else in the EU at the very least. Given within a relatively short amount of time, the use of miles for non-trivial distances practically disappeared. Now it's only used in colloquialisms (e.g. "it's a few miles away") or for familiar distances (e.g. "the graveyard is a mile that way"); anything else is km, and sooner or later we'll likely be using km everywhere.
I think you can forget that "sooner" part. Colloquialisms are very, very, stubborn. For example, German and Dutch still have the word "ellenlang" (http://en.wiktionary.org/wiki/ellenlang), literally "ells long", but typically used to describe durations (a long boring talk can be 'ellenlang'), even though the meter has been the unit of length for almost two centuries. Similarly, "miles long" is still in use for long, tedious or annoyingly large distances.
The UK took a while and still hasn't switched some units. Our speed limits are miles per hour; beer on draught in pubs is sold in pints and half pints (and it is not legal to sell it in other units even if clearly labelled with conversions).
I know that, I'm from Ireland. However, in comparison to the US, the UK is practically France as far as metrification goes. We still sell by the pint here too, and people still use imperial units casually (mostly inches/feet for human-relative distances, pounds/stone for people's weight, and pints for draught beer and cider) but everything else is metric at this point.
The UK should probably bite the bullet as far as roadsigns and speed limits go. It's about time, really.
Just an interesting aside, measurements in construction are almost always given in either metres or millimetres, never centimetres (at least in Australia.)
So that would be 914.4mm and 1219.2mm respectively (or 1.2192m I guess).
The wisdom of this was explained to me by my builder father that metres and millimetres are orders of magnitude far enough apart that you can usually figure out which is which without too much difficulty in a specification even if they are not annotated properly. Centimetres fall close enough to inbetween that it can be confusing. Plus only using two standard units of measure (one for small stuff, another for large) is less potential confusion then using three.
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In Australia we started metrication in 1971[1] with 1974 being the effective tipping point when all road signs were changed.
Being born in the early 70's, I have a rough understanding of imperial measurement units. I can roughly understand if something is a few inches or a few feet, but can never remember how many inches in a foot, and have no concept of relation between feet and miles. Miles I understand as a bit over 1.5kms. The only length measurements we tend to still give in imperial is a person's height in feet and inches. The concept that over six foot is tall, and under five is getting to be short (for men at least) has such utility that it's stuck. Official documents will use metric though, usually centimetres.
Weight is similar. Kilograms rule, except when talking about the weight of newborns which will still often be given in pounds and ounces informally. But give me anything else in pounds and I have no idea (very frustrating when that happens in movies.)
Similarly Celsius rules. I know 100°F is a hot day, but wont boil an egg, and 0°F is colder than a mother-in-law's kiss, but those are rough approximations, and anything between those two I have to convert.
Gallons is a foreign language.
However all the colloquialisms such as giving an inch and taking a mile are still common.
And yet somehow despite all this, the world continued to spin.
It's not like America is the only country that will have ever transitioned. Many other countries have gone through all those issues without much complaint. It's not some untested experimental process being advocated.
It's not like the US is going to be using weird-arse inches, furlongs, horses and stones forever.
Wow you must not have read my comment at all. I explicitly said we should convert, but that there are some considerations that need to be made. I even said that now is a better time than ever.
Perhaps I'm not being zealous enough with my "hey lets be careful about this as we do it" type statement?
Now isn't going to happen and later might be better. We're transitioning more and more to computers. The transition could be handled more easily if we have a generation of computer programs that can easily handle either. Pervasive language support for units would probably help.
America is like the fat kid who's the last to jump into the swimming pool; everyone else is shouting the water is fine, it's warm, it's fun, but you're sitting there worried about the consequences of being wet. As if you were the first person to ever get wet.
You don't need to be careful. Just look at everyone else who jumped in without injury and jump yourself.
Yep. Nope. You've outed yourself in an unfortunate way. Everyone wants to do business in the US and everyone is prepared to jump through the hoops to do that business. US regulation accomplishes a bunch of things, including adding friction to non-US companies doing business in the US.
With that hyperbole, I'm willing to bet you've never stepped a foot outside the USA. Don't you realise it also adds friction for US companies doing business in the everywhere else?
From an economic standpoint, the rest of the world is a big enough market so that it's worth supporting too. And everybody gains when markets join.
About tooling, yeah that's bad. But everybody has 2 sets of tools all over the world, because both US and rest of the world are big markets. A transition won't change a thing, the only thing that changes is that a few decades from now, everybody will stop needing one of those sets.
Paper is also already a nightmare. All equipment supports both ISO and US standard, and is more expensive because of that.
Constuction aparell is always weird. Your 36" doors are certainly not exactly 36" wide, as metric 90cm doors are not exactly 90cm wide. At least here (at Brazil, thus metric) there are several different sets of sizes to choose from, because some people want bigger doors and windows, other people want smaller ones.
I think you overestimate the costs at the US, and underestimate the benefits.
> * Tooling that exists in standard units seems to be a bit of a red herring: I dislike having to own wrenches in both standard and metric units - a transition to one set would actually be nice. At a larger scale, i.e. manufacturing, it would make sense to start replacing things with metric on regular maintenance cycles. With very long cycle things just having a label change.
I don't think you'll get rid of that second set of sockets/wrenches for decades. There are going to be just too many instances where there is an old connector, nut, bolt, etc. that needs to be worked with. I think of it as having two sets of wrenches or am buying two sets of wrenches anyway. The metric and imperial sockets come in one set and share the ratchets.
But it shouldn't be all or nothing. For example, although most of the world uses the metric system, I think in aeronautics they still use feet to measure altitude. US could migrate to metric independently of the aeronautic standards.
Additionally, I don't think that changing tooling should be a priority. Even in the countries that use metric system, we use nuts and screws measured in inches. They are usually called 1/4, 1/2 and so on ignoring the "inch" part. Also, in Venezuela, letter is the standard paper used, not A4.
I think a good solution would be for the US to use metric to measure most of the things people and industries interact with (distance, velocity, weight, volume), but you can keep the old measures when convenient.
The amount of nuts and screws measured in inches that you use is probably inversely proportional to your geographic distance from the last remaining non-metric industrial nation in the world.
We don't come across them quite as much in the Antipodes. :-)
I am not sure, if the paper sizes (A4, ...) are belonging to the metric system ... but of course, here a standardization would be nice. At least software producers seem to know (most of them) now, that there are also other formats as the "standard US formats".
A0 is a square meter, and everything in the A series has an aspect ratio of sqrt(2) and different sizes are achieved by simply folding (or cutting) in half. It's actually pretty neat... check out:
The reason: I don't think, that this fact is essential to the A series. It is neat, yes, but when do you have A0 paper in your bureau? (When you are not in the printing-business).
The thing with cutting in half is more essential to it, than that it is based on square meter. Also, even when it is an square meter, the sides are something "odd" because the ratio is fixed.
They're not part of the metric system, simply based on it. The 1:sqrt(2) ratio used is extremely convenient as it scales up and down nicely, and the other series are such that an Ax sheet fits nicely into a Cx envelope, and a Cx sheet fits nicely into a Bx envelope.
How are factors of 2 and sqrt(2) "based on metric"?
At some level you could say that the U.S. measurements are "based on metric" since almost all of them are defined in terms of metric units. You just have to apply the proper factor (which is a decimal, but a terminating one --- unlike the sqrt(2) business).
I never wrote that the factors were based on metric. ISO paper sizes are based off of an A0 sheet having an area of 1m². That's it.
The 1:sqrt(2) ratio has to do with subdivision. An A0 sheet subdivides into two A1 sheets, which subdivides into two A2 sheets, and so on. 1:sqrt(2) width/height ratio used in ISO pages sizes allows this, which makes dealing with paper significantly easier when it comes to slicing up pages, folding, packing, &c.
By that standard, the U.S. liquid measures could also be described as "metric". 2 cups->pint, 2 pints->quart, 2 quarts->pottle (rarely used, more commonly called a "half gallon"), 2 pottles->gallon.
You appear not to understand the actual utility behind the page width/height ratio used in ISO/DIN page sizes.
Also, the word "metric" has a very precise meaning: that of being part of the internationally agreed system of decimal measurements. The thing you've mentioned don't fit that definition, and US customary units are simply defined in _terms_ of metric units, but are not metric units themselves.
> By that standard, the U.S. liquid measures could also be described as "metric"
The ratio has nothing to do with metric. The base sizing of the A0 page is, on the other hand, defined as having an area of 1m² in that regard, DIN/ISO paper sizes are _based_ on metric. However, _never_ did I state that they _were_ metric.
So no, by the standard that I gave, you _couldn't_ say that US customary measurements for liquid measures could also be described as "metric".
Go back and read my original comment. The first sentence was this:
> They're not part of the metric system, simply based on it.
Here I was making reference to A0 sheets being defined as having an area of 1m², thus the sheet sizes are _derived_ from metric, not _part_ of the metric system.
The next sentence was a _completely_ independent statement about the utility of the page ratio used in ISO/DIN paper sizes:
> The 1:sqrt(2) ratio used is extremely convenient as it scales up and down nicely, and the other series are such that an Ax sheet fits nicely into a Cx envelope, and a Cx sheet fits nicely into a Bx envelope.
I can't fathom how you somehow got from an innocuous pair of statements about paper sizes to powers of two in US customary measurements for liquids somehow being "metric".
Ok. I'll be super explicit about this. The page measurements don't matter. What matters is that all the standard page sizes have exactly the same width:height ratio when halved or doubled to obtain the next size up and down. That's the magic property that the 1:sqrt(2) width:height ratio used in the ISO/DIN page sizes gives you. The fact that an A0 sheet is defined as having an area of 1m² is a distraction. It's the width:height ratio that matters.
Your comparison to liquid measurements misses the point. It's irrelevant. Your statement that the US units are defined in terms of US units is irrelevant.
What is relevant is the preservation of the width:height ratio between pages sizes in the ISO/DIN paper size series.
"That's the magic property that the 1:sqrt(2) width:height ratio used in the ISO/DIN page sizes gives you."
Which is very similar to the "magic property" that you get when you have measuring units that are powers of two rather than factors of ten. So, no, I"m not "missing the point" at all.
That you think this is "irrelevant" indicates to me that you haven't done a lot of cooking.
Yes you are, because _this has nothing to do with factors of ten vs factors of two_. This is nothing to do with US customary units vs metric. _The units are irrelevant._ That's what you're not getting. What is relevant is that the same page width/height ratio is maintained between the different page sizes.
You touched on what I see as the biggest most long term piece to transition, American tool and die companies, foundries and fabricators. A lot of these companies are based around giant machines with 20 or thirty year life cycles. Switching to metric would be a factory's worst nightmare short of blowing the place up.
Those mile roads often have odd names like "18 Mile Road" or "12 Mile Road", so even after a transition it wouldn't be especially hard to track (I'm guessing you are subconsciously tracking the numbers, not measuring on your odometer...).
The survey system is a bigger thing to deal with, but it isn't something people confront day to day either. I've seen deeds using geographic coordinates to describe plots, so there is also a relatively straightforward path to not dealing with it.
I think, even, when the US is changing to the metric system, the bigger problem will still linger around (and when I have hope for the the metric system, I don't have any for that):
How on earth can we make the British driving on the "right" side of the street.
I was in high school when the US planned to switch to the metric system, then suddenly the deal was off. I never learned why, and I was too busy playing D&D to care.
The article is right, though; metric measures are easier to work with. I will vote in favor of changing.
The last road sign I've seen in metric was one on I-95 northbound, just north of the I-26 interchange. Sadly, SC DOT changed it out a few years ago and now it just reads in miles.
I understand there's a road in Arizona that is still signed in metric.
Really does not paint a true picture. Living in the UK I use metric for everything except driving distances, driving speed and measures of beer (pints).
And what measurements are still signed / represented in some way in imperial measurements in the UK? Road signs, speedometers and beer at a bar in a pub. Everything else is presented in metric and everybody I know uses metric for everything else.
Ah but your different opinion/use of measurement does highlight how gradual these kinds of change can be - similar to changes to word meanings over time. I didn't say everyone does.
Milk is still sold multiples of pints, with the litre value listed.
I don't think it's anywhere near that bad. It's a gradual transition and it's working (imho).
In my mind, miles for roads is really the only standout left. I don't think of pint as a measure, but the name of a particular type of glass.
Outside of that I've just never found a practical use for the imperial system. It's bad enough trying to translate things to american and back, let alone trying to keep track of a US gallon being 4/5ths of an imperial gallon ..
The pint glass is a perfect fit for 500ml of ale. If you tip it into the glass with a modicum of care, you end up with the head not quite reaching the top.
(Of course, had we switched to 500ml glasses, leaving ale in 568ml bottles, we'd be stuffed. A point to bear in mind if contemplating a piecemeal transition.)
It's still a transition that's slowed down. I guess it's a generation thing. People I know still talk about baby birth weight in pounds and ounces and height in feet
As a member of the younger generation, I rarely think in imperial and I think the same is true for most of my social group at least.
For example:
- I struggle to visualise feet or inches, we always used metric units at school so metres and cms are what I understand
- kilograms for weight is much more natural to me than stones or ounces (really, I have no idea how much an ounce is, although I kind of know a pound is a small bag of sugar-ish)
- miles are probably the only imperial unit I'd use, but even still, I find km much easier to reason about, perhaps because I have lived in Europe in the past.
- oh, and the trusty pint of course!
In US schools are children taught metric or imperial? For example when measuring a liquid for a science experiment are measurements made in millilitres?
It depends on the class, but most are taught both. At my school, almost everything in the science classes was done in metric, though we were of course very familiar with imperial.
When we're young we're taught the imperial method since it's the customary system. Once we start getting into science classes it's all metric. Still, outside of science classes (and the military) we don't use it at all.
Which means we don't have a good working model in our heads of what a kg feels like or how warm a 30 degC day is...that sort of thing. I think most Americans have a pretty good feel for what a liter is since lots of drinks sell in that volume (and it's almost the same as a quart). But I think it'll be a cold day in hell before we cook in metric...customary units are pretty handy with home-style cooking since they line up pretty well with the size of stuff that's already in your kitchen (a cup, a teaspoon) and all our measuring and cooking equipment is in imperial. Actually, converting imperial measurements is a rotten mess, but using them in practice is pretty convenient. The sizes of most things just sort of intuitively makes sense on a human labor sort of scale (a pound of food turns out to be a nice filling meal, you can estimate inches with your thumb and feet with your forearm, 0 degF is colder than frozen water and just at the edge of tolerable, while 100 degF is just at the edge of tolerable on the other end of the scale even if water it nowhere near boiling, a pint is a good size for a beer, a yard is about a man's reach, an acre is about the size of a field a person can work in a day, etc.) -- there's some sense to them.
The military uses metric for most things however (due to constant international collaboration) and you'll find military people have a better grasp of the feel for most metric units, especially distance.
It's a bit like in England though where metric is taught, but people still colloquially refer to people in stones or distance in miles and beer in pints. Actually lots of countries still use their customary measurements [1] in certain niches, Koreans still use the pyeong 평 [2] when dealing with real estate for example.
I've been fortunate enough to travel quite a bit to metric using countries and have developed enough sense to quickly convert in my head. I know what a good room temperature is (22-24 degC), but I have no idea if I should bring a jacket when the weather is 15 deg C or not and the difference of 30 - 40 deg C always catches me by surprise. I have good feel for ml, cl and liters (lots of wine drinking), an okay one for kph, meters and km (driving and walking most places).
But g and kg continue to stupify me since I can't seem to find a useful frame of reference for those measures. I just end up mentally doubling all kg to pounds where it makes sense. I mean, what common thing weighs a kg? Everything at 1 kg just seems to be too heavy and to make use of it you end up sectioning it into grams, the liter is the same, too much liquid for anything useful, except I can usually split 1000 ml of wine with my wife over a long relaxing dinner and that's my reference point. And I guess that's the problem, I end up using fractions in decimal countries like I'd use them in the U.S. (most imperial units have handy fractions: 1/3, 1/4, 1/2, 1/12, but metric countries work better with decimals.
> what common thing weighs a kg? Everything at 1 kg just seems to be too heavy
I'm back from a mall so... 1 l of water is 1 kg. 1 l of wine too, for any practical purpose. Water is usually sold in 1 l bottles or 500 ml in restaurants and automatic machines. Pasta is usually sold in 500 g or 1k g boxes. Milk, sugar, flour and salt too. Oil and vinegar are usually 1 l. Butter is usually 250 g or even 125 g for smaller doses. Sure not many items seem to weight more than 1 kg but weight your clothes, you'll be surprised how heavy winter clothes are :-)
Basically everything is priced either by the kg or by the liter (vegetables, cheese, meat, beverages, toothpaste, etc). It's required by law so we are able to compare different products of the same kind and different weight and get the better deal, quality aside. Obviously the label has a bigger figure for the price of the item than for the price by the kg.
As you see, whatever the units are they a convenient for everyday use because all the economic and legal system is consistent with them. A transition in a country as large as the USA would be bumpy. I'd like to see it happen before I die but I won't bet anything on it, not until they are surpassed by some other country as the leader of the world. After that there might be some real economic incentive to a switch.
Amusingly, the areas where the most US Americans are familiar with SI are gun calibers and recreational drugs. [n] (OK, I may have a warped sense of humor, but it's true)
Great, maybe it will spread to other countries :-)
Actually I'd like to see the actual width of the screen (bezel included) rather than the diagonal, which is pretty useless. It's to the width that I've been looking at recently when I wanted to know which TV fits into the space I have for it.
What is that 20°C? Why is that a better number than 68°F?
I'm not arguing against metric in general, I'm arguing that the temperature part of it is just kind of thrown in there because they were both used in France.
No one wants to carry the political risk of trying to replace the ALL-AMERICAN measurement system, I suppose. I wonder if there are any pro-metric lobbying firms that exist...
Not to derail the conversation, what how good can a political system be if their too scared to bring something up for fear of the public when its in their own interests?
Seems like an extremely common political reaction to having to cause your voters hardship or annoyance. To name one easy example, you persistently see this reaction across all the economies of the EU regarding the on going economic crisis, whether it's regarding subsidies or spending cuts or social programs or retirement or immigration.
I'd argue there are exceptionally few political systems on the planet that deal with such well.
In democratic systems, we generally trust the people to know their own interests, and when they're wrong win them over with debate rather than ignoring them.
democracy is not having a referendum for each random decision or new law. It's electing (thus giving your consent) someone to unilaterally make changes for everybody else during a short time. This person has the responsibility to take the hard decisions that individually would not come around.
ex, when death penalty was abolished in France, it was in opposition to the majority of french people. A few decades latter virtually everybody now agrees that's the best way of things and that it was a great decision. At the time it was a politically courageous enforcement.
The benefits-- which would be far greater than the metric system (more difficult too)-- would come from having a universal language, regardless of what it was. And English is surely the best placed; being the world's second language, where not the first.
All I know is don't walk into a Canadian Subway and ask why they still sell sandwiches by the 6" and foot. I made that mistake once and offended everyone in the place
Good luck trying to change something that's part of a cultural identity.
Irish are catholic not because religion is actually something positive, but because it's a contrast with the British church, and part of their cultural identity.
> Irish are catholic not because religion is actually something positive, but because it's a contrast with the British church, and part of their cultural identity.
Hmmm, I think you'll find that Catholicism is older than the Church of England (not that this relates to the metric system in any way). The English changed from being Catholic to Church of England during Henry VIII's reign. The Irish largely remained Catholic.
Catholicism started as a counter reform to Marcionism, including the Torah again in the Bible and rejecting some Gnostic concepts still prevalent in Paulism.
This was at least a century (the dating is not precise) before Saint Patrick converted Ireland to Christianism, and specially, many centuries before the creation of Church of England.
I don't see what part of my observation about 21 century Ireland made you think that I presupposed the Church of England was older. That part of history is even on TV (The Tudors).
0 and below - Freezing. Wear a warm jacket and closed toe shoes or boots.
1 - 10 - Cold. Wear an overcoat (a light one if you are used to colder weather)
10-15 - Early spring time. Long sleeves are probably in order, maybe even a sweater.
15-20 - Late spring. Wear short sleeves.
20+ - Warm to hot. Wear short sleeves. If it gets to be 24+ shorts are appropriate.
I am deliberately not giving conversions to Fahrenheit here because I think that's how you just go back to using it. Try to internalize the metric system here.
The second challenge is to switch your clocks/watches to the 24 hour mode. Not strictly metric system related, but you will not have to worry about AM vs PM again.
For the advanced users: switch your car to show your speed in km/h instead of m/h.
For the super-advanced users: try to figure out how many liters per 100 km does your car consume :).
Edit: if you cook (and you really should), use a scale set to grams instead of measuring cups for any recipes you are making. Almost all foods list both oz's and grams on them. You will get much more accurate measurements this way and will learn to gauge what 150 grams of cheese looks like, etc.