I like this paragraph from the article. Sort of first principles approach to the whole thing :) "The basis for the whole system is the A0 format which has an a

I like this paragraph from the article. Sort of first principles approach to the whole thing :) "The basis for the whole system is the A0 format which has an area of one square meter. With an aspect ratio equal to the square root of two, a sheet of A0 paper ends up being 841 × 1189 millimeters. Figuring out the dimensions of the subsequent paper sizes does not require any real mathematical strain since each ensuing size can be created by simply folding the paper in half with the crease parallel to the shortest sides. If you do this with an A0 sheet of paper, the resulting dimensions will be 594 × 841 millimeters, or the A1 format. Take note that the height of A1 is equal to the width of A0"