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Comment by adamrt | Hacker News Reader

The amount of time and money to shift at this point would be astronomical wouldn't it? It would take a few generations as we would continue to have to teach imperial so people could convert when they ran across any existing media referring to the imperial system measurements.

Hundred years of machines that use imperial, speedometers, odometers, books, tools, software, air conditioning, heating, manufacturing, construction, plumbing, including regulatory codes for each of those.

Not saying its impossible and it's definitely my knee jerk reaction, but at this point I cant imagine it being feasible.

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It's really not that bad. Canada did it in the 1970s and it's still around, and we didn't revert to the stone age or anything.

SI units are already in wide use in the US, for instance for electricity (Amperes, Watts, Volts). For the most part, international trade has pushed US industries to adopt metric anyway: metric fasteners are used all over, in cars for instance. Also, countries that have switched still use inch-pattern stuff; in Canada we still use NPT threads and imperial size pipes with no ill effects; even in Europe they still use some imperial-threaded stuff.

My favourite is car tyre sizes. 215/60R16 means the maximum width is 215 millimetres, the aspect ratio of the cross section is 60 percent, R is both a separator and a code for radials, and it's made for 16 inch rims.

Even in the Netherlands, a staunchly metric country, bicycle tyre diameters are measured in inches. (Wouldn't know about car tyres.)

We were almost there in the 1970s.

As for "a few generations", yes, certainly. We have only to look to the mishmash of unit use in the UK.

But what's wrong with taking a few generations to get there?

Turning it around, we got rid of a lot of specialized units - hogshead, chain, furlong, peck, etc. (If Peter Piper picked a peck of pickled peppers, how many many more are needed to make a bushel?) So it's clearly possible.

Also, metric countries still use non-metric terms for some cases, eg, "inches in a screen", the market price of a "barrel" of oil, and food energy in "[food] calories". This tells me that the transition can occur piecemeal.

>metric countries still use non-metric terms for some cases, eg, "inches in a screen"

This is an example of American influence. Decade ago it was in centimetres.

For example, in this 2004 Siemens commercial for Russia CX65's screen size is 13 square centimetres:

https://www.youtube.com/watch?v=2ZaY_f6U8Mo

If Imperial keeps getting used, it will get even harder to get rid of it.

What kind of argument is this? "It would really hurt to amputate my leg, so let's just wait and let the gangrene go further for now."

> What kind of argument is this?

"it's definitely my knee jerk reaction"

I think it might not be as bad as we imagine. All speedometers I've seen show both miles-per-hour and kilometers-per-hour, all thermostats I've seen have an option for switching to Celsius, all scales I've owned can display both pounds and kilograms (my current one even has an option for stones), all measuring cups I've seen in a long time have both systems displayed, etc. Even lumber wouldn't necessarily be a huge issue. After all, the "2 by 4" is actually 1.5" by 3.5", which equates to 38mm by 89mm. Would it be a huge deal to round that to 40mm by 90mm?

And, in any case, most people have a mobile phone now which can quickly do unit conversions. I really think it actually is feasible, if you could get the public behind it (good luck).

You're not thinking about all the designs, tooling, manufacturing facilities, etc to build all that stuff though. That's where the real cost is.

> Would it be a huge deal to round that to 40mm by 90mm?

It actually would be a big deal to round things like that I think. Whole designs would need to be updated to take into account the new dimensions of things.

Any manufacturing component which cannot easily be adjusted to a slightly different measurement is poorly designed, in my opinion. I would expect that much of these tools could be tweaked to produce things in metric measurements. If not, the dimensions can simply be converted and re-labeled. If something manufactures a square piece of metal that is 3" by 3", is it a huge deal to just document it as being 76.2mm by 76.2mm?

> Any manufacturing component which cannot easily be adjusted to a slightly different measurement is poorly designed, in my opinion.

Imagine all of the parts in a car engine. Everything fits together perfectly. Engine mounts line up in the right places. It all has to be very precise.

Now imagine you take all those parts and round them off a bit. Nothing much, just a mm here and there. If you try to put the engine together with these parts, it's not going to work at all.

Also consider that you can't just simply convert the units. Take a 5/16" socket wrench for example. Nobody makes a 7.9375mm socket wrench.

While I think the rounding would work with lumber, I definitely don't think it would work with things like car engines. For such precisely-measured components, converting to a metric measurement with the correct significant figures should be fine.

Repair shops can maintain tools for both systems (they already have to). For converting, I mean the dimensions of a component, not tools and fasteners that need to work with tools. Those would likely take a "metric only going forward" approach.

Rounding from 38 to 40 is a difference greater than 5%. Some applications might support that, but I'm sure there are plenty that won't. For example, wood joints have very small tolerances.

> You're not thinking about all the designs, tooling, manufacturing facilities, etc to build all that stuff though. That's where the real cost is.

A lot of them are already metric.

More manufacturing is done in China, and the factories are used to the different international markets because they're often parts suppliers for foreign companies that have their designing done in various countries. So they're well equipped to make things in either inches or mm.

You're overstating it, there are only 2 other countries in the world that use imperial units

If you changed the sizes of lumber, I'm pretty sure that someone would come out with "new inch" tapes that were labeled with inches and feet but accounted for the change in size (spreading the extra millimeters out across the distance).

The dimensions in use are something that people are very used to working with and they know how to do the necessary mental arithmetic to work with them.

Luckily, the easy mental arithmetic is a main benefit of the metric system. I really doubt people would create "new inch" tapes. They would probably hang on to existing measuring tape for personal projects though.

The imperial choice of using highly composite numbers is at least as convenient for mental arithmetic as decimals.

What's 1/10th of 3 3/8"?

27/80. Asking HN seems like a roundabout way of getting the answer, though.

I-19 in southern Arizona has its distance signs in meters and kilometers as part of a test during the '70s. There have been plans to change it for a number of years but local opposition has stalled it.

https://en.wikipedia.org/wiki/Interstate_19

If I remember correctly, raw lumber here in Finland is in inches and planed lumber in millimeters :)

We did it in the UK. Its fine.

Apart from some things like miles and gallons which would require a massive synchronised change that is.

I'd also like it if we drove on the RHS here as well so we can get decent import vehicles.

> Apart from some things like miles and gallons which would require a massive synchronised change that is.

It's less the synchronisation and more the expense of replacing all road signs throughout the kingdom, making it a political non-priority.

I'd happily help foot the bill.

So how much is that 1000 mile journey going to cost?

1000/44.94.4561.119= where's my calculator?

Of course it's going to be hard. Changing legacy code always is. But this kind of argument seems to be presented in the US for everything from gay marriages to gun control laws.

If you really want to, you can do it. And it's not as painful as presented especially since many countries have done it (https://en.wikipedia.org/wiki/Metric_system). And the longer you wait the more painful it becomes.

Isn't the United States in practice a worst of both worlds approach where you have both imperial and metric measurements inconsistently mixed together?

Doubt it.

The separation is mostly distinct, at least to me. We mostly use imperial and in science class and such we use mostly metric.

The worst of both world I've seen was England.

They're mostly metric until you drive their car and then they decide to use mile per hour. That's pretty random...

https://en.wikipedia.org/wiki/Road_speed_limits_in_the_Unite...

While the article doesn't flat out say it but if you stare at the uk speed sign image and the comment below the image you will see they are in fact in MPH.

edit:

found an article about it:

https://en.wikipedia.org/wiki/Metrication_in_the_United_King...

Yes. The mix in the US is a disaster: http://www.cnn.com/TECH/space/9909/30/mars.metric.02/

The total cost to switch has gotta be in the hundreds of billions of dollars. Has anybody done such a calculation?

What's the total cost of not switching? I'm willing to bet it's in the tens of billions each year.

All your major trade partners use the metric system: EU, China, India, Australia.

Thing is, we use both systems now. What huge cost is involved by saying "Starting in 2020, the metric system will be the official unit of measurement in the US." Manufacturing companies can switch as soon as they want to. Most consumers' toolsets already have both systems (wrenches, sockets, etc).

"Metrication Matters" (Google TechTalk from 2007)

https://www.youtube.com/watch?v=NgtsSM7vN0M

It starts a bit slow but stick with it. I'm currently rewatching it after several years so I'm not sure there is a calculation. I think there is. A lot of the production in the US already is metric so it shouldn't be that expensive.

Remember that everybody else also had to change their (many) measuring systems over to metric. It went remarkably well.

My estimate is "approximately zero". For example, people talk about the cost of converting road signs as though we have pick a Tuesday in March and switch the entire country that afternoon. How about we adopt a policy like "when we install new signs or replace old ones as routine maintenance, we make them metric - and here's a conversion chart so we're all using the same mile-to-km rounding."

The Australian experience (as told in the "Metrication Matters" video) was that a "direct metrication" where everybody switches at the same time and doesn't try to maintain two systems at the same time is fast (about a year) and cheap (often saving money).

Road signs can be prepared in advance and covered. The covers can be removed quickly. Another option is to put stickers on the road signs on Metric Sunday.

> My estimate is "approximately zero"

You do realize there is more to switching to metric than just updating the road signs, right?

Think of all the military and space technology that uses inches.

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