Don't forget my favorite size, "statement". This is half of letter size. Sometimes used for small statements, sometimes used as letter folded.

Hacker News users may be familiar with Julia Evans (http://jvns.ca) who creates technology zines that work in both A4 and Letter sizes, folded in half.

I used to work at Kodak and they had an industrial printer division in my building. They would go through pallet-fulls of A4 for their testing. Only place Ive seen it in use in a business setting in the US.

> legal (letter but longer)

This one surprised me quite a bit. I think most people have A4/letter-sized folders. Why does anyone think that papers slightly longer than those folders are a good idea?

Legal size folders exist and are widely used by people who use ... legal size paper.

Legal folders can be great to be able to print letter-sized things on, then you have an area at the bottom to write notes and stuff.

I'm just about old enough to remember (in the UK) foolscap paper, an imperial size also a bit longer than A4. You never see it any more (at least I don't) but foolscap sized box-files are still readily available. I guess a slightly bigger box than you need is not usually a problem.

Foolscap is just half an inch below legal - and I bet having a box a bit larger than what you're putting in is a selling point, not a hindrance.

Huh, this explains why some of my older teachers would call a4 pads as foolscap pads. I guess the paper size had been updated by the time I got to school, but their terminology wasn't.

Many filing cabinets in the US are also sized so you can put letter sized folders in one way, or rotate the folders 90 degrees and legal sized folders will fit correctly.

> Legal size folders exist and are widely used by people who use ... legal size paper.

Sure. But I didn't know I use legal size paper or even what it is before I asked the apartment complex to print the lease agreement, and it didn't fit in their own folder with the other move in papers. In my rank of weirdness discovered upon moving to the US, this is at about the same level as the different ounces.

And by “nearly everything”, I've never personally seen or used printer or copier paper that wasn't letter or legal. I know it exists, but I've never, not once, bought or used it.

> legal (letter but longer)

Why are two slightly different standards needed? Does legal really need to print "just a little bit more" text than others? If so, why not just use that one for everything?