International Standard Paper Sizes

Markus Kuhn:

In the ISO paper size system, the height-to-width ratio of all pages is the square root of two (1.4142 : 1). In other words, the width and the height of a page relate to each other like the side and the diagonal of a square. This aspect ratio is especially convenient for a paper size. If you put two such pages next to each other, or equivalently cut one parallel to its shorter side into two equal pieces, then the resulting page will have again the same width/height ratio.

Same principle as the using the square root of 2 to achieve a very similar aspect ratio on both the iPhone Duo’s inner and outer displays. With the international paper system, you can do things like scale up 2× or scale down 0.5× without changing the relative margins. E.g. print or photocopy at 50 percent to get two virtual pages per printed page of output. It’s an elegant system.

★ Saturday, 26 September 2026