Metric units in stores

ObjectMike

I've been playing with an app idea that in part deals with taking in measurements. I was going to let the user select their units (ft, cm, etc) but I'm not sure what I should use for metric. I poked around at some online stores that used metric and looks like a healthy mix of cm and mm (with a bit more in mm it seems?) is used and rarely, for "regular" consumer sized stuff, do I see meters used. Is there a rule of thumb of when what metric unit is used? Is it by item type? Size range?

GuyWhoKilledBear

@ObjectMike said in Metric units in stores:

I've been playing with an app idea that in part deals with taking in measurements. I was going to let the user select their units (ft, cm, etc) but I'm not sure what I should use for metric. I poked around at some online stores that used metric and looks like a healthy mix of cm and mm (with a bit more in mm it seems?) is used and rarely, for "regular" consumer sized stuff, do I see meters used. Is there a rule of thumb of when what metric unit is used? Is it by item type? Size range?

According to the woodworking YouTubers I follow, Europeans use millimeters (not centimeters or other fractions of a meter) to measure linear dimensions of furniture. I would bet that the rule of thumb is to use kilometers for distance to travel and millimeters for anything else.

Arantor

I’ve seen a lot of mm used over the years, cm used to be more common but I think the trend is to use mm for most things.

We do tend to stop using mm once you get much past a meter or two just because writing “2500mm” is a bit weird and you don’t normally need to be that precise.

Same as with liquids really, different parts of Europe do it differently - here in the UK anything under a litre is written in ml, anything over a litre is written in litres (e.g. 1.5l) with a few exceptions where for whatever reason they write both l and ml units.

Across the channel though, it’s a different story, where things written in cl is (or at least was) more common. E.g. bottle of wine here is 700ml, but 70cl across the water. I have even seen the odd thing measured in dl but that’s really rare.

If you’re making it user selectable, I’d say to just put in mm, cm and m and let the user decide what makes sense for them and their use case.

I would note that the metric market is (vastly) larger than the imperial market so catering to the different denominations is probably better for a broad appeal app - the total population using imperial is, officially, America, Liberia and Myanmar leaving metric for everybody else… (unofficially, older people in the UK still use imperial too)

Gurth

It depends on where you go. In the UK, almost everything seems to be measured in millimetres — they say things like “This plank is 2000 mil[limetres] long”. In more normal parts of Europe, that would usually either be a plank of 200 cm or a plank of two metres, depending on desired/perceived/understood accuracy. But when you’re talking about something like the width of a room, few people would say it’s 452 cm, let alone 4520 mm — they’d more likely call that 4.52 m in everyday life.

Like @Arantor says: let the use choose which they prefer.

But really, this is no different from US measurements: when do you use feet and when do you use inches? Some people would say it's a six-foot plank, others would call it a 72-inch plank, so letting the user choose there as well also seems the sensible solution.

Carnage

For Sweden, the unit used as the one that is the best fit. We don't say 2000mm, unless in schematics, but 2m mm, cm, dm, m, km and Swedish mil is all in common use, same for weights and volumes. ml, cl, dl and l. Above that m³ is used though.

Applied Mediocrity

@Carnage I haven't seen dm and dl used all that much here, but yeah.

PleegWat

There's definitely context involved as well. Anything involving construction is going to be in millimetres, both on schematics and in dimensions of parts. Otherwise, centimetres or metres are more common.

I'd second putting in multiple options - millimetres, centimetres or metres for the metric crowd; feet, inches, or feet and inches for the US customary people.

Gribnit

@ObjectMike said in Metric units in stores:

I've been playing with an app idea that in part deals with taking in measurements. I was going to let the user select their units (ft, cm, etc) but I'm not sure what I should use for metric. I poked around at some online stores that used metric and looks like a healthy mix of cm and mm (with a bit more in mm it seems?) is used and rarely, for "regular" consumer sized stuff, do I see meters used. Is there a rule of thumb of when what metric unit is used? Is it by item type? Size range?

Don't depend on consistency here for there will be none. Change the design accordingly.

Kamil Podlesak

@Arantor said in Metric units in stores:

the total population using imperial is, officially, America, Liberia and Myanmar leaving metric for everybody else… (unofficially, older people in the UK still use imperial too)

I can't believe no reacted yet: this is not a list of countries using imperial units, it's a list of countries not using metric. They are not same: Myanmar does not use imperial measurements, it uses its own units.

Now, with the important part done, let's look at the issue at hand:

@ObjectMike said in Metric units in stores:

I've been playing with an app idea that in part deals with taking in measurements. I was going to let the user select their units (ft, cm, etc) but I'm not sure what I should use for metric. I poked around at some online stores that used metric and looks like a healthy mix of cm and mm (with a bit more in mm it seems?) is used and rarely, for "regular" consumer sized stuff, do I see meters used. Is there a rule of thumb of when what metric unit is used? Is it by item type? Size range?

mm vales have a distinct advantage of not using decimal comma or point --> you don't actually need to worry which one is the correct one. Just make sure your localization library does not decide to use thousands separator! Actually, if possible, it is a good idea to force a short space as a thousands separator; it will provide very convenient visual help for values in range of meters, while being completely unambiguous (nobody's using decimal space AFAIK).

There are countries where cm might be preferred in some areas (for example: person height), but every literate person can handle mm.

One important caveat: this assumes that the precision is sufficient or at least the values are properly rounded. Value like 1422mm ± 100mm is just plain stupid!

Applied Mediocrity

@Kamil-Podlesak said in Metric units in stores:

Myanmar does not use imperial measurements, it uses its own units.

nga mutha

Literally "five mutha", but in fact it is only four.

Muthafuckers.

remi

@PleegWat said in Metric units in stores:

There's definitely context involved as well.

I fear that this is the most important part and that there is therefore no possible generic answer to the OP.

Even just thinking about my own country, almost any of the (sub)multiples of m from mm to km might be used in different applications (anything below mm would be for specific scientific tools, and I don't think anything above km is ever used).

Here, everyday items tends to be in cm, or m when larger than 1-2 m. For example a frying pan diameter, or a sheet of paper, or a wooden plank. But anything that's more "technical" (whatever that means...) than "everyday" will tend to be in mm (or m). For example a screw, or a wooden plank.

And if you've noticed the repetition, well done and read back the first sentence of this post. Which means that even if you let the user picks one, you may find that in some cases they would actually have expected something else.

So I would say make your system flexible (so you can tune things later on), but don't over-think it () because you will not get it Right, unless you're dealing with a very specific type of objects (but if you were, you would probably already know the customary units).

dkf

@remi said in Metric units in stores:

I fear that this is the most important part and that there is therefore no possible generic answer to the OP.

The unit used will often be the one that minimises the number of apparent significant figures.

remi

@dkf But referring back to the conclusion of my previous post, the operative word in your sentence is "often."

In other words, yes, it's mostly the case, except when it isn't. And there's no rule about it.

Filed under: language is hard, let's go shopping

Gurth

@dkf said in Metric units in stores:

The unit used will often be the one that minimises the number of apparent significant figures.

But usually skipping things like dm, dam and hm for most purposes. If not for that, it would be simple enough: using whichever only gives one digit before the decimals would probably cover over 90% of all use if all the units were used.

cvi

@GuyWhoKilledBear said in Metric units in stores:

According to the woodworking YouTubers I follow, Europeans use millimeters (not centimeters or other fractions of a meter) to measure linear dimensions of furniture.

IKEA seems to use centimeters on their website.

(Where else would you get your furniture? )

remi

@cvi Furniture (IKEA or other) is always in cm here, except when it is in m. Consequently, wooden planks are mostly in m, or cm. Except when it's more aimed at professionals (carpenters etc.) where it might be in mm. Or when one dimension is much smaller/larger than the other (e.g. a stud), when it might be a mix of... any of the three (e.g. "10x40x2.4" for a stud of 10 mm x 40 mm and a length of 2.4 m).

I recently ordered a new kitchen, all the technical plans are in mm (that is, except plans drawn by the architects that are in m!), but when talking in shop with the sales guy everything was in cm. That is, except a few things (such as the thickness of the worktop) which was in mm. Or when we talked about the overall dimensions where we used m. Usually it's the one (out of mm, cm, m) that has the less digits before the separator, except that when we add up stuff we don't necessarily switch units (so one kitchen unit is 60 (cm), two are 120 (cm), not 1.2 (m)).

And that's all just talking about furniture and building material.

ixvedeusi

If you want a heuristic, I'd propose the following as a starting point:

Start out with a set of choices according to the dimension: For distances, km, m, cm, mm might be reasonable choices, and if you think you'll ever need it add μm. Volumes are generally m^3, l, ml; though as stated above cl and dl are sometimes used, and I think I have seen the hectoliter in the wild.
Discard all units that leave you with zero digits before the decimal point. If that would leave you with no choices, use the smallest of the units you just discarded.
Discard all units that give you more than 2 digits after the decimal point. Again, if that leaves you with no choices, use the smallest one.
From the remaining units, choose the one with the least digits after the decimal point and the least trailing zeros before the decimal point.
Allow the user to choose a different unit, and always indicate the unit!

Zecc

I'm going to say it: picking the right unit is less of an issue in metric than in US customary.

Anyone looking at 120 cm will just as easily interpret it as 1.20 m or 1200±5 mm without even realizing it.

Centimeters is a good default. Meters if we are talking about measuring tapes (since they are usually integer multiples of meters) or longer; millimeters if we are talking about drill bits or screwdrivers, or other precision stuff.

(But yes, writing 12 dm would be weird. Decimeters are rarely used, for whatever reason.)

cvi

@remi It's indeed not terribly consistent.

But I also think that it doesn't matter much. Converting between different prefixes is very easy. 205mm being 20.5cm? No problems. 207cm being a bit over 2m? Yeah, also not exactly a huge mental effort. I'd say something like 2070mm isn't very common in general, but it wouldn't be a problem if e.g. IKEA's page said that either.

Edit: 'd, it seems.

PleegWat

@ixvedeusi said in Metric units in stores:

I think I have seen the hectoliter in the wild.

Just for raw milk, I think.

@ixvedeusi said in Metric units in stores:

If that would leave you with no choices, use the smallest of the units you just discarded.

I can't think of any household objects which are measured with sub-millimeter accuracy.

ixvedeusi

@PleegWat said in Metric units in stores:

I can't think of any household objects which are measured with sub-millimeter accuracy.

This is true (even more so if you also include μm...) but I learned long ago that just because I can't think of something, that doesn't mean that it doesn't exist; an algorithm should cover all edge cases.

Apart from that, I don't know what the specific use case is here, so I wouldn't want to assume that it a) only has to cover household items or b) only has to cover distances.

remi

@PleegWat said in Metric units in stores:

@ixvedeusi said in Metric units in stores:

I think I have seen the hectoliter in the wild.

Just for raw milk, I think.

And other foodstuff liquid, I believe. I remember seeing stuff about wineries (and breweries) and it's customarily measured in hL.

But that's really starting to get into specialised fields (and their units), it's not really general-purpose in any sense of the term. If you go this way, you have to account for biologists who will use μm (or maybe even nm), or farmers who use hectares for surface (=1 hm^2) and quintals (=500 kg) for weight, or whatever else. But if you work in those fields and you have to ask us about the units to use, well you're , and horribly so.

Anyway, @ObjectMike never said in which domain the app will be, even just a hint of whether it's woodworking, cooking, miniature aircraft modelling, clothes or whatever would be the actual starting point in picking a unit. And besides, I agree with the previous posts that, as long as the unit is clearly visible (and you don't change too often which one you use for comparable things!), any of [mm, cm, m, km] will do. At worst it will feel a bit jarring/unusual to the user, but that's all.

Gurth

@ixvedeusi said in Metric units in stores:

I think I have seen the hectoliter in the wild.

In wine production.

da Doctah

If you're really serious about using SI units for everything, please note that next month I'll be turning 2gs old.

I'll expect cake.

HardwareGeek

@da-Doctah Congratulations. I passed that milestone recently (for some definition of recent; I'm not going to say how recent it was — perhaps yesterday, perhaps "recent" in geologic time), but I didn't realize it until I just calculated how old that is in more common units.

Edit: I am between 2Gs and 2Gis old.

PleegWat

@HardwareGeek For comparison: The unix epoch is about 1.6 Gs ago.

cvi

@PleegWat Is that 1.6 gigaseconds or 1.6 gibiseconds?

Arantor

@cvi said in Metric units in stores:

@PleegWat Is that 1.6 gigaseconds or 1.6 gibiseconds?

yes.

LaoC

@Applied-Mediocrity said in Metric units in stores:

@Kamil-Podlesak said in Metric units in stores:

Myanmar does not use imperial measurements, it uses its own units.

nga mutha

Literally "five mutha", but in fact it is only four.

Muthafuckers.

Shortchanging people on unit conversions seems to be popular; any Brazilian (I'm not sure about their Portuguese cousins) will tell you "15 days" when they mean two weeks.

Zecc

@LaoC said in Metric units in stores:

I'm not sure about their Portuguese cousins

We do. Namely when talking about "in 15 days" or "15 days ago".

The reasoning, I guess, is that we include today as well as the homologous weekday in the next or previous fortnight.

So "15 days from now" would be:

See? 15 days, Friday to Friday.

Same goes for 8 days vs 1 week.

I think we also casually say "in 30 days" when referring to a month, regardless of its actual size, but that's just being

Also, don't ask me why we talk about "15 days of vacation" when we mean two weeks (10 work days)

And yes, it is weird and the sort of thing a curious child grows up questioning before shrugging it off.

Gurth

@LaoC said in Metric units in stores:

Shortchanging people on unit conversions seems to be popular; any Brazilian (I'm not sure about their Portuguese cousins) will tell you "15 days" when they mean two weeks.

Many (most? all?) Romance languages count days inclusive while Germanic languages count exclusive.

BernieTheBernie

@Gurth And what about 1 week? In german, we say 8 Tage (literally 8 days) - is dutch different?

da Doctah

@Gurth said in Metric units in stores:

@LaoC said in Metric units in stores:

Shortchanging people on unit conversions seems to be popular; any Brazilian (I'm not sure about their Portuguese cousins) will tell you "15 days" when they mean two weeks.

Many (most? all?) Romance languages count days inclusive while Germanic languages count exclusive.

And then there's the traditional "octave" of seven notes (the eighth is a repeat of the first), matching musical notation for transposition by full octaves; the usual symbol is a clef with "8va" above or below it, but greater transportations reveal that there are only seven scale degrees when they affix "15ma" and "22ma".

This pretense is not observed in the chromatic scale. Everyone agrees it's twelve notes and the thirteen one is the repeated one.

ixvedeusi

@da-Doctah said in Metric units in stores:

the traditional "octave" of seven notes

interval names are the worst of the worst and a perfect example for why 1-based indexing can DIAF.

HardwareGeek

@ixvedeusi It's confusing, but it kinda makes sense if you consider that the most fundamental interval — the "interval" between a note and the same note — is the unison. They're the same, so there's a "unity" or "oneness" between them, so there's an interval of 1 between them. The next note up or down becomes a second, and so on.

Where it really gets confusing is modified intervals. Some intervals (second, third, sixth, seventh) have two qualities, major and minor. Other intervals (unisons, fourths, fifths, octaves) have three, perfect, augmented and diminished. Add to that (in equal temperament tuning) the same interval has multiple names, e.g., an augmented fourth is exactly the same as a diminished fifth. (In non-equal temperament tunings, they are almost exactly the same.)

Gribnit

@Kamil-Podlesak said in Metric units in stores:

mm vales have a distinct advantage of not using decimal comma or point

False, at least for ammunition, and probably also for wrenches.

ObjectMike

It's an app for tracking garden planting history. Both as an excuse to play with Android development and to have an app that works the way I think about the problem. I assume metric users have similar oddness as US customary users like me: a raised garden bed might be 4ftx8ftx16in and that's how I'd want to enter it into such an app (and not convert the others to inches or the 16 to 1.333ft). The idea of a floating point number of meters seems odd since I'd never do floating point yards. At the same time measuring in hundreds of inches instead of feet seems odd but apparently metric users don't mind hundreds or thousands of cm or mm. Maybe it's more consistent in each metric using country but when I've looked at online stores it seemd all over the place.

dkf

@ObjectMike said in Metric units in stores:

At the same time measuring in hundreds of inches instead of feet seems odd but apparently metric users don't mind hundreds or thousands of cm or mm.

It's very easy to convert between the different metric distance measurement units in your head, and that's one of the really big advantages of the metric system. (The other advantages come when you're doing things with lots of units and you want to try to limit the number of calibration constants, but that's very much not an everyday thing.)

Gurth

@BernieTheBernie said in Metric units in stores:

@Gurth And what about 1 week? In german, we say 8 Tage (literally 8 days) - is dutch different?

It is: for something that happens a week from now, 7 dagen is the expected number, not eight. “Ik zie je over zeven dagen weer” (“I will see you again in seven days”) would mean Friday the 15th (as it’s now Friday the 8th).

@ObjectMike said in Metric units in stores:

I assume metric users have similar oddness as US customary users like me: a raised garden bed might be 4ftx8ftx16in and that's how I'd want to enter it into such an app

Sure, an equivalent would be something like a 1 m × 2 m × 50 cm garden bed, and people would/could/might call it that: length and width in metres, height in centimetres.

The idea of a floating point number of meters seems odd since I'd never do floating point yards.

That’s because you have these odd subdivisions that have their own names, and are used to thinking in them. Anyone used to metric will just mentally shift the decimal separator and use either measurement interchangeably. I suppose in much the same way that people used to American customary units doesn’t really feel “1 foot” and “12 inches” are different and may use them interchangeably depending on the situation and personal preference.

when I've looked at online stores it seemd all over the place.

See above: because all it takes to “convert” between different subunits is to move the decimal separator, there is no difficulty at all and people will do this on the fly. And that’s why different sellers may use different units, because to the customer, it’s basically all the same.

If I were to see, for example, a sofa advertised as being 238 cm wide, I would just know right away, without actively having to think about it, that it fits in the 2.5 metres I’ve measured between the walls in the room where I want to put it.

Benjamin Hall

@dkf unless you're my students, for whom it was deep black magic.

Gribnit

@Benjamin-Hall said in Metric units in stores:

@dkf unless you're my students, for whom it was deep black magic.

I don't call 10 a convenient base and neither should they.

Zecc

@ixvedeusi said in Metric units in stores:

1-based indexing can DIAF.

If I had to pick between using 0-based indexing and 1-based indexing, I'd pick 1-based indexing 1st.

PleegWat

@Zecc You do you. I'd pick 0-based 0th.

da Doctah

@Gribnit said in Metric units in stores:

@Benjamin-Hall said in Metric units in stores:

@dkf unless you're my students, for whom it was deep black magic.

I don't call 10 a convenient base and neither should they.

It's common, but 2.718281828 is natural.

Carnage

@Gribnit said in Metric units in stores:

@Kamil-Podlesak said in Metric units in stores:

mm vales have a distinct advantage of not using decimal comma or point

False, at least for ammunition, and probably also for wrenches.

Never used a wrench that needed decimal values of mm. If that would be necessary, micrometers are probably used instead, but then you're probably out of wrenching range of tools anyway

HardwareGeek

@Carnage I think I have some sockets that have increments of .5 in small end of the range, like 3.5 or 4.5 or something like that, but I'm not sure I've ever actually used those small ones.

Carnage

@HardwareGeek said in Metric units in stores:

@Carnage I think I have some sockets that have increments of .5 in small end of the range, like 3.5 or 4.5 or something like that, but I'm not sure I've ever actually used those small ones.

Yeah, true, those do exist.

Arantor

This topic reminds me once again, how the dualist nature of mankind works.

That on the one hand we have evolved sufficiently to make precision tools for our uses to assemble, disassemble etc. and rise above the rest of the planet in ingenuity etc.

And on the othee, how fucking clever we are to make measuring things this fucking complicated.

izzion

@Arantor said in Metric units in stores:

how the dualist nature of mankind works.

?

Gurth

@Arantor At least we’re now at the lower end of the historical number-of-units-in-use-worldwide curve, so we must be doing something right. Well, except for the Americans, Liberians and Myanmarese, obviously.