Comment by echoangle a day ago
A4 isn’t some random format, you can derive it with three pieces of information:
A0 is 1 square meter
An to An+1 means cutting the paper along the middle of the longer edge
Each An has the same aspect ratio
Those are pretty useful properties and precisely define the dimensions of A4.
True, but I don’t understand why this would make letter size confusing to Americans. European office workers are not sitting around marveling at the mathematical elegance of the definition of A series paper. It just doesn’t matter in daily life.
> It just doesn’t matter in daily life.
Like a lot of mathematics it does matter in your daily life but you actually just don't think about it because of course this works - unless you're an American and so no it doesn't.
The A-series paper sizes mean everything scales very naturally. Poster? Pamphlet? It's just the same ratios again but bigger or smaller. There is a single design where this works, and that's why the A-series exists, you can't just pick anything, only this works.
Can you explain concretely why it matters in daily life that I can cut the paper posters are printed on in half several times to wind up with paper of the size that letters are printed on, and that these have the same aspect ratio? Why would I ever want to do that / why should I care that it's possible?
I'm not trying to be combative; I genuinely don't know.
Not the paper, the stuff on the paper scales the same. Want a large poster and then also handbills to give out? They're identical. Got 15 full size sheets of colour information but now want to turn it into a pocket handout ? No problem, it's the same thing but smaller.
This feels obvious - of course it works like that, until your paper sizes aren't using this ratio (which the US ones don't) and then the frustration is apparent.
Not only that but C envelope sizes match the A size. So an A4 piece of paper fits a C4 envelope flat.
A4 folded in half (size of an A5) fits in a C5 envelope.
An ISO standard that makes sense and isn't based on different professions like "letter" vs "legal" vs "folio" and other US sizes.
But also the reason that, for example, screens have 80 columns, (also related to punch cards), but that was about the width of a "letter" page at 10cpi.
> A4 isn’t some random format, you can derive it with three pieces of information …
You can derive letter paper with two pieces of information: 8½ and 11. Just having a laugh, of course — I do admire the A/B series, even if I wish that they were based on a square yard :-)
Not sure where you got “random format” from the comments, but we (U.S.) also use a very precise method for defining the size of paper, which is 8.5x11 and legal as 8.5x14. For the US, both are sized to fit in the same standard envelopes. I’ve never thought, “boy, I really need half this sheet length-wise but made shorter to keep the same aspect ratio for this situation”, so while I can understand why that could make sense when creating an international standard, it isn’t more or less random or more/less precise than any other basis. Our basis simply evolved naturally from our system of measurement and our needs with countries we traded most closely, rather than as an international standard based on a different system of measurement that needed to be shared among numerous countries situated closely together.