
AsK HN: Why can't the US change to the metric system? - robomartin
Every 3.14 years I have this question. I know that changing all highway signs would cost a lot of money and would take a long time. Well, had we started fifty years ago we would have been done by now.<p>When designing mechanical components or circuit boards (or looking at other's designs) one recurring thought is that our fractional unit system might actually cause inefficiencies and increased cost of goods.<p>You can look at an American design product and identify it as such by taking a few measurements.  Mechanical designers will think in fractional terms and specify "nice round numbers".<p>For example, a feature might be set to 1/16 of an inch, when, perhaps, a smaller thickness or length would have worked just fine.  In this case 1/16 is 0.0625 in, which happens to be 1.5875 mm.  Now, a designer working in SI units will probably specify 1.5 mm for the same feature.  This doesn't seem like much, but you are talking about 5.5% more material.  That's not a trivial amount if you are making a bunch of widgets.<p>We ship liquids in gallon containers.  A gallon is 3.8 liters.  If we worked with liters, might we buy and ship three liters instead?  Perhaps generating less waste?<p>This is a very simple example to illustrate one of   the mechanism that might be at play here.<p>Don't know.  Just a though in between coding sessions on a fine Saturday evening (Los Angeles).
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reuven
When I was in 4th grade (in 1979), growing up in the US, we learned about the
metric system. My teacher said that we were learning it, because the US would
soon be switching over to it.

I came home and told my mother what my teacher had said. And my mother
responded, "Yes, that's what my teacher told me in 4th grade, also."

Fast forward more than 30 years, and the US is no closer, despite other
countries (such as England and Canada) having pulled off smooth transitions.
Aside from a few signs on a highway in Massachusetts (of course) that I saw 20
years ago, marked in km as well as miles, and 2-liter bottles of soda, the
metric system has completely and utterly failed in the US.

I now live in Israel, where the metric system is standard. My children cannot
believe that I once used a system that wasn't so simple and standardized. But
because they're not _learning_ the metric system, but just using it, they
never learned the beauty of its design, with powers of 10, and uniform
prefixes. They just know how many cm tall they are, how much is in a 1 kg
container of ice cream, and how many km it is to their grandparents' house.

It seems obvious to me that the metric system can and should be uniform,
including in the US. But there is so much inertia, and so much history of
opposing it, and so much technology tied up with the existing English system,
that I don't realistically see it happening anytime soon, even if it could and
should happen.

~~~
eli_gottlieb
Hello fellow _oleh amerika'i_.

Funny thing is, there's one metric unit I truly don't like: temperature.
Fahrenheit-scale temperature is just _better_ for describing the immense
ranges of cold and heat you'll see inside the average year in a very temperate
place like the United States or large parts of Europe. Only over here in a
warm climate like Israel does Celsius make sense, where zero degrees is
actually one of the coldest temperatures of winter and forty degrees the
hottest temperature of summer.

For distances, I don't really consider Imperial _or_ Metric that much more
useful. They're just slightly different.

~~~
flog
Never in my life, which ranged from living in tropical jungles to snowy
European cities, have I ever felt the desire for differences in measuring
temperature.

Comparing F and C is one of the most obvious cases for metric, as I see it. 0
is freezing, 100 is boiling. It couldn't be clearer.

~~~
wglb
Ah, but what it it when it is -40?

~~~
wglb
P. S.: This is a trick question.

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humbledrone
There are many extremely valid arguments for why the US should change to the
metric system, but I don't think that "maybe we'll round down and be more
efficient" is one of them.

> We ship liquids in gallon containers. A gallon is 3.8 liters. If we worked
> with liters, might we buy and ship three liters instead? Perhaps generating
> less waste?

Might we buy and ship 4 liters instead? That's closer to 3.8. Anyway, if we
rounded down to 3, what about those people who really need 3.8 liters? They'll
buy two jugs, which is double the packaging, and if they don't need the extra
2.2 liters, it's a waste of the liquid.

Also, many things are sold by the pound. But a pound is ~0.45 kilograms.
Surely by your reasoning people would round up to 0.5 kilograms, and thus be
less efficient.

~~~
robomartin
I see your point and raise you 0.35mm.

In working on a design I specified 1/4 shafts. Why? Well, from the commonly-
available range of sizes this is what met the specs.

Then I went to price manufacturing. No issues here in the 'States. My Chinese
CM comes back to me and says I can save money if I go with a 6mm shaft rather
than 6.35mm. The 6mm shaft is more common, weighs less and costs less per unit
length. And so the entire design slowly changed to metric units and we saved
both money and weight.

Of course, this is a loose and probably really flawed hypothesis with nothing
but personal data points and random observations for support.

~~~
humbledrone
Your hypothesis is that all common measurements in imperial units round down
when expressed in metric units, and that somehow by switching and rounding,
"efficiency" will be gained, and therefore metric units are superior.

Please think about this for a moment. Really think about what you are saying.
It's ridiculous.

~~~
snogglethorpe
Er, I'm not him, but I suspect the reason 6mm shafts were cheaper is because
that's what the rest of the planet orders (not anything to do with rounding or
whatever)... Rare or custom specs almost always increase the price.

~~~
humbledrone
robomartin is the OP -- read his original post and also the comment that I was
replying to. It doesn't matter that in some circumstances rounding imperial
units to the nearest-but-lower metric equivalent results in cheaper parts
(perhaps due to better availability). What I'm saying is that it's absurd to
use that as an argument for switching from imperial units to metric.

(Don't get me wrong, imperial units are completely backwards and horrible, and
I would love for the US to switch. It's just that this particular argument for
doing so is stupid.)

~~~
robomartin
Well, it's only absurd because my data points are easy to attack. I'm with you
on that. It would be very interesting if a study looked at various efficiency
metrics to compare the systems.

Like I said, I know my argument is weak and calling this idea nonsense at this
stage is probably not without merit. At the same time I've seen this effect
more times than I can remember in my career, which leads me to believe there
might be a number of cases where it may very well be factually correct to
assume that imperial is costing us money and creates more waste.

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jared314
The US is on the metric system[0]. The people, however, are not. The children
use the United States customary units, because their parents use it. The
parents use it, because their parents used it. The companies use it, because
the people use it.

I also happen to like the orderly ISO 216 paper sizes, but US people don't use
that either.

[0] <http://en.wikipedia.org/wiki/Mendenhall_Order>

~~~
bazzargh
Never mind the paper sizes, the really crazy US measurement is the paper
density: <https://en.wikipedia.org/wiki/Paper_density>

tl;dr - most of the world uses grammage (g/m^2, ISO 536). The US uses pounds
in a ream of paper in its uncut basis size. The basis size varies with the
type of paper, and so does the ream size. It's a measurement that can only
make sense to people who never take paper out of the box.

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rogerbinns
Perhaps the biggest thing non-metric people miss is easy conversions. A litre
of water weighs one kilogram and occupies a 10cm cube. This makes it really
easy to move amongst volume, weight and dimensions.

It is already the case that many goods sold in the US are labelled in both
imperial and metric. The order can just be switched on labels. In theory the
roads could be left using miles as has happened in the UK.

Clive Cussler used to have a preface in his books saying this: "Please forgive
the inconvenience of converting measurements from what most Americans are used
to. But in 1991 the United States finally became the last nation on earth to
convert to the metric system."

He has long since given up.

~~~
mtviewdave
>Perhaps the biggest thing non-metric people miss is easy conversions. A litre
of water weighs one kilogram and occupies a 10cm cube. This makes it really
easy to move amongst volume, weight and dimensions.

Indeed. And while that's very useful for scientists and engineers, it's not
really useful for the average person. Most people don't do conversions often
enough to justify switching their measuring system to metric, and if one
doesn't care about doing conversions, the advantages of the metric system
become much less clear. And the American government isn't going to switch the
country to metric unless it provides clear advantages to most Americans.

~~~
rogerbinns
I blew a friends mind when he mentioned wanting to have a rainwater tank that
contained some number of gallons. I immediately said how much it would weigh
and what the dimensions of the tank would be, and consequently how it would be
too large for the area he intended.

It drives me nuts trying to follow recipes written by Americans as the
measurement units are entirely random between weight and volumes. Sometimes it
makes sense due to packing - eg flour is more accurate by weight than volume.
But often the worst one is used.

~~~
waps
Why not switch to a system that's based on actual physical constants instead
of properties of a certain impure water mix ?

How about we start measuring distances relative to c, mass in GeV/c2, or maybe
in multiples of electron masses, and so on and so forth. Sooner or later
(probably much later, granted) we'll do this, so why not get ahead of the game
?

~~~
nitrogen
The meter _is_ defined in relation to c:
<https://en.wikipedia.org/wiki/Meter#Speed_of_light>

~~~
waps
Well, yes, but read that page. I mean a vaguely reasonable fraction, not
1/299792458 per second (plus if you're going to be pedantic, second still
isn't defined in terms of c).

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zokier
Gallons, inches and feet etc are fairly easy to handle. I've grown up in a
completely metric country and yet I have fairly good intuition of most
"imperial" units, mostly due spending time on the internet. Changing those
would be pretty low on the list of things to change in the US. Here are some
things I'd change first.

Date formatting. This is such a major pita when you see something like
02-03-04 and you have no clue what date that's supposed represent. At least
with customary units, the units are usually specified but no such luxury with
dates.

Paper sizes. This is annoying because converting between Letter and A4 is not
trivial. You might end up with cropped or scaled pages, or with a printer
waiting you to load Letter sheets to tray. That latter is very annoying when
a) the printer is in other side of the building b) how to cancel the job is
not obvious c) the "error" blocks the whole printer while you try to sort it
out.

(Prime) Fractional sizes. While inches are fairly intuitive to me, and
something like 1/4" is still good, I have no clue how much something like
7/32" is.

MPG for fuel consumption. This is arguably just a bad way to evaluate the
economy of cars. Just swap to GPM (gallons per mile) if you want to keep your
customary units.

Confusing list prices. The way sales tax and tipping works in the US is weird.
Life is just simpler when you can just pay what the price is. It's also bit
difficult to compare US prices to rest of the world prices.

Clothes sizing. Well this one applies to the whole world, but could we please
sort this out someday? Of course it's bit funny to see something like "US: L,
FR: S", but the funniness vanes out quickly when you try to find clothes that
actually fit you.

In conclusion it is not the units that are the problem, but the way they are
used.

~~~
jordn
If wanting to fit with stereotypes i think "US: L, FR: S" was meant to be the
other way round.

MPG may not be a great measure but people generally have an easier time
understanding 'bigger is better' so i think it works better than GPM.

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aaronbrethorst
Because Congress and Ronald Reagan:
[http://lamar.colostate.edu/~hillger/laws/usmb.html#disbandin...](http://lamar.colostate.edu/~hillger/laws/usmb.html#disbanding)

    
    
        “The efforts of the Metric Board were largely
        ignored by the American public, and, in 1981,
        the Board reported to Congress that it lacked
        the clear Congressional mandate necessary to
        bring about national conversion. Due to this
        apparent ineffectiveness, and in an effort
        [by President Reagan] to reduce Federal
        spending, the Metric Board was dis-
        established in the fall of 1982.”

------
stevep98
If there's anything that will cause the US to change to metric, it's the
inefficiencies in manufacturing. Nothing we make to a non-metric spec can be
exported. We have to duplicate production lines and tooling to build a metric
version of anything. That is inefficient.

------
michaelpinto
Nassim Taleb argues that the metric system is too abstract for people to
relate to as where measurements like an inch (the size of your thumb) are much
more easy to relate to. And as someone who studies usability I have to say
that he's on to something.

~~~
mav3r1ck
To this day I still don't remember the exact number of feet in a mile. I know
between 4-5 thousand, but the exact number is just absurd.

~~~
mikiem
exactly 5280. Its not absurd. It has always been that number.

~~~
justincormack
The mile has not even been the same size, it changed in 1959
<https://en.wikipedia.org/wiki/Mile> and it still is not at sea, where the
nautical mile is longer. The Roman mile was 5000 feet.

~~~
mikiem
I stand corrected.

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LarryMade2
Well in my growing up 70s-80s in primary/high school, We got metric courses a
few time and some of the books covered it (did you know that a meter is
roughly three feet, the distance from the floor to a doorknob? I learnt that
in school.)

In the early 80s there was another push many California road signs had dual
postings of miles/kilometers to destinations. Cars also had dual gauges on
their speedometers, large soda bottles were now in liters instead of ounces.

Then... it stopped again.

Wikipedia fills in some of those blanks
[http://en.wikipedia.org/wiki/Metrication_in_the_United_State...](http://en.wikipedia.org/wiki/Metrication_in_the_United_States)

I myself would like to see it change over, it would be a pain for a year or
so, but then everything is standard with the rest of the world.

~~~
mindcrime
Yeah, I remember the same deal in the 80's. In Middle School out teachers made
a point to tell us that the US had switched to the Metric system, and taught
us all about metric units, etc. And, as you say, road signs often had both
units, car speedometers had both, etc.

And then it just stopped. No notice, no noise, no nothing. Everybody just
stopped talking about it, the road-signs went back to all Imperial
measurements, car speedometers dropped km/h readouts. As far as I can tell,
the only real legacy of metrification in the US is that anybody who does much
tinkering with mechanical "stuff" that might involve bits that are imported,
needs a toolbox loaded with both Metric and SAE sized tools. To be honest, I
always half figured the whole Metric movement was arranged by Craftsman, Mac
and Snap-On in order to double the volume of tools they sold.

------
skryl
For the same reason that we're all still on 12 months, 30ish days, 24h, 60m,
60s, 1000ms time.

~~~
mcintyre1994
When you put it like that, it's a bit weird. Is there an imperial fraction of
a second that somehow never caught on?

~~~
evolve2k
This is because our system of time is based the earth circling the Sun and
works best for things to slice up a circle, 360 degrees, base 6.

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vyrotek
While we're at it. Can we have the whole world switch to UTC time and stop
dealing with timezones and daylight savings?

~~~
rtkwe
I agree that DST is just madness but timezones are less insane in theory, they
would make sense if they were determined by the longitude normalizing time so
that sunrise and sunset happen at roughly similar times. Currently they're
pretty screwy sure but the idea actually has some merit.

One thing to consider though is that switching everyone over to UTC you'd
still have to consider local business hours. However, instead of just looking
at their time zone and figuring 9-5 or standard hours you'd have to have a
listing of each business's UTC hours. It might fracture more than timezones do
currently.

~~~
dreeves
Here's my argument for why DST is a good idea: <http://messymatters.com/dst/>

~~~
tarre
Everyone I have talked with about DST has had opinion, that the time to be
chosen as base time used around year is the summer time. I would also change
daylight at summer from 5am to 8pm, but i would also rather have in winter
daylight at 16pm than 8am

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aj700
Yes, that'd be lovely. No more talking about lbs and such. (I'm British but we
were not taught imperial measures.)

But they'd still be saying things like

* "Where's Chechnya?" (if under 15 in 1995 you have an excuse)

* "I love being in England", when they're standing in "Glassgau" (Glasgow=Glazgo) - try it. Brave!

* "different than", "gotten", "color"...

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laurencerowe
Change to imperial units instead, just think of that extra 95ml of beer in
every pint glass!

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drill_sarge
1 Cubic Foot = 7.48051948 Gallons [Fluid, US]

1 Cubic Foot = 6.42851159 Gallons [Dry, US]

1 Cubic Foot = 6.22883545 Gallons [UK]

meh

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lazyjones
I ask myself often why we still use inches in the EU: for pipe diameters (we
still use NPS instead of DIN), trouser sizes, TV/LCD diagonal sizes (that
seems to be changing)...

------
eip
<http://www.youtube.com/watch?v=Xw9lTB0hTNU>

