the A series · from A0 to A6
Built as a memo rather than a table: the thing worth hanging it up for reads across the room, with the full reference in smaller type below it.
Three sizes in one archive — from a sheet on the fridge to a poster on the wall.
Fold a sheet in half across its long side and you get the next size down. A4 folded gives A5.
Everything else follows. A0 has an area of 1 m², and each next size is half the one before.
For the half to keep the same shape, the sides must be in the ratio 1 to the square root of two. No other number works.
That is why you can fold the sheet in half forever and the proportion never changes.
Why the numbers can be trusted. Every countable number here is computed from data rather than typed in, and the sheet must pass 3 independent checks before it is allowed to build — how many items there are, the order they come in, and the claim in the highlighted box itself. If one fails, there is no file.
