From the taking-it-a-bit-too-far department:
Probably you know that a European (ISO) A0 sheet of paper is one square meter, and that successive sizes are half the preceding, so that an A1 is an A0 folded in half, down to A7; A4 is the standard ‘letter’ paper. The standard is very consistent, such that the weight of a letter can be calculated by the size of paper used, copying machines all can auto-fill multiple pages, and the like. This is really convenient.
I just found out that German toilet paper is A6 sized.
