The international paper system is surprisingly easy to learn. There is A0 which is big, A1 which is 1/2 of A0, and A2 which is 1/2 of A1. And so on down to A34 which is the size of the meat patty in a bargain hamburger. Some of those meat patties are actually printed on A34 paper in inkjet printers…
The odd thing is who made the decision about where the system should start – A0 is 841mm x 1189mm but that doesn’t even work out to be an even number in imperial measurements. I have a horrid feeling that one of the dimensions may be no more scientific than an even division of the distance between the inventor’s home and the nearest public house.
Does it get better? No. They have B and C sizes and these are also derived from the dimensions of a ferret. Not the big ferret, the small, twisted one.
I will say that the multiplication system for the paper is clever – and once you are into the A3, A4, and A5 sizes they can be useful for most modern paper purposes – but you are still going to find that nothing ever fits the loose-leaf binder that the shop that sold you the paper also sells. This is one of the rules of the stationer’s game. The better sort of shop can make you sad and discouraged in imperial, legal, international, and Japanese terms on a variety of surfaces. The 3/4 US Legal cold pressed three-hole archival matte is popular if only because it is nearest the door and you can buy a ream and run for it before it all becomes too much.
It won’t fit, of course, but it does scrunch up nicely.