In moving from EU to the US, the biggest difference I noticed is the reliance on fractions over decimals. 1/4th of something as opposed to .25. That’s probably what I miss the most about using the metric system on a daily basis.

Using fractions sounds great, I think fractions have a human quality and are a more natural way to approach numbers. In writing, I think putting down 0.5 is slightly jarring compared to the better ½, at least in non-technical contexts.

One classic trick to estimate a proportion is to do it as a fraction. It might be hard to tell that someone ate 44 % of a pizza, but significantly easier to judge that they ate a quarter and three quarters of the next quarter (which is 7/16 which is 44 %.)

That said, as soon as I need to do any arithmetic on the number (including compare it to other numbers) I convert it from fraction to decimal.

I think this is also a case of just being more familiar with something, I find "1/2" or "3/8" much harder to parse than "0.5" or "0.375" (having grown up in the EU).

Totally agree. And how does it work when you measure a thing and it is 1,35 inch do you in the US convert it to fractions? And how then do you find this fraction?

A ruler sold in the US (and Britain, on the reverse/bottom) has inch markings with fractions.

│.╷.|.╷.│.╷.|.╷.│.╷.|.╷.│.╷.|.╷.│

0⅛¼⅜½⅝¾⅞1

So the measurement, when taken, is 1⅜".

I've seen inch rulers with different fractions, e.g. one end might be eights, the other sixteenths, turn it over and there are tenths.

(I don't know how this works with digital measuring devices — I grew up in Britain so have never used inches professionally. Only in Warhammer and TV screens.)

With digital devices I assume there is a mode switch like in the digital scales I have at home in the US. I actually work in grams for things like bread making which seems easier than a combination of pounds and ounces.

I think I want my writing to reflect how I talk or think about it. So if the spoken sentence is "specification is a half millimetre" then write with ½ instead of "0.5" because the former will be read out correctly.

But that’s my point! The way you talk or think about it is absolutely influenced by what you’re used to, and what you’ve grown up with.

To you, it’s obvious and natural that „half” is 1/2.

To me, it looks off and I have to „convert” it in my mind to 0.5, which is the way I think about it.

Exactly this. A “half” in my mind translates to 0.5. I don’t do any conversion, 0.5 exists as the very concept of “half” in my brain.

A foot being 12 inches makes fractions work really well in US units (as well as a mile being 8 x 10 x 11 x 6 foot). And with it working so well, many people don't seem to be able to imagine to work without them.

In metric a meter isn't as nicely divisible. Of course we get around that by subdividing 1.2m or 1.5m instead (or 0.8, kitchens and lots of furniture is designed in outer dimensions that are fractions and multiplies of 0.8 meters). But that only works well if you write them out add decimals, because saying "this cupboard is 1/2 0.8 meter wide" is just silly

The metre is not used for everything. The standard for construction and manufacturing is the millimetre. In the UK a standard kitchen unit is a 600(mm), with 300 and 900 varients. Appliances come in 500, 600 and 900 widths, that being the gap or unit they (should!) fit into. It would feel unatural to me to say 0.6 etc for a unit. These common dimensions are used like nouns, "You need 3, 600s" rather than "You need 3 units 600mm wide" tying them more closely to language and perhaps then harder to change.

I agree. I’m from Europe and being trimmed to metric through and through. My main issue with the us or imperial units is not so much the conversion factors and weird rules. It’s the simple fact that I have no feeling how hot or cold a given temperature is, how long or short a given measurement etc. Just being exposed to the system and trying to live with it helps. Sure one still converts all the time mainly to get a familiar value to compare too. But after a while that doesn’t really matter. In the end it’s mostly important if for example is 80F a warm day or not? Is 1,5miles a long walk? Etc. Sure adding ease of use when calculating with units is a different thing. But I understood that woodworkers etc like to measure in 8th/1000th of an inch. Something I would need to be exposed for years to be able to do.

In the US I have the same issue with Celsius (plus the degrees are bigger). But I assume I could fairly easily spend some time to mentally align the scales and develop the intuition from there if I spent any time using Celsius day to day.

> I think a lot of it is just that - familiarity.

True. For example, as an European I'd obviously have some difficulties expressing sizes in inches and feet, but I'd have some difficulties too if I was buying a new monitor or TV and the clerk asked me the screen size in centimeters.

Well, from my own experience if you have to fit a TV set in a given space (e.g.: between two libraries) you go to the shop with the width and height of that space in centimeters and you don't care much about the diagonal in inches. You buy the largest screen that fits.

Yeah, oddly enough, TVs and monitors are measured in inches diagonally even in Europe.

However, in the aforementioned scenario (buying a new TV), the correct answer is always: "the biggest you have".

Same in Japan, though they're usually not called "inches". So my TV size is "65 series".

But "the biggest you have" is not the right answer for TV size: if your room is small and your TV is too large, it's uncomfortable to view it. The TV needs to be sized according to the viewing distance. Usually, this isn't an issue for most people: too-large TVs are usually outside their budget. But this is changing, as bigger and bigger TVs become less expensive.

You are right.

What I mean by that comment is that people might come to a store and think: "Wow, this 65" TV is huge, I don't need that". But they are forgetting that when watching a movie, a lot of screen space is unused, because the aspect ratio is different (those black bars on the top and bottom).

So, if you can fit the TV somewhere, it's always a good idea to pick a larger one than you think you need.

After 10+ years in the US, I now find A4 a bit weird (narrow and tall), so +1 to your point on familiarity.

Yeah, like humans don't have ten fingers. Hint: 10, so what are those people thinking? ;-)