Design Stories

There’s more than meets the eye in every Paper-Oh notebook. Get insider details on our design decisions and inspirations here.

Why We Love International Paper Sizes


There are three key characteristics that define every Paper-Oh notebook: Expressive paper texture, unique book binding and international paper sizing. The visual and tactile benefits of high-quality materials are obvious, but why do our Paper-Oh designers have such a love for these specific dimensions?

Simply put, the dimensions of ISO 216 (as the international standard is now known) are mathematically, well, simple! The standard is based on an aspect ratio of the square root of 2 (1.4142), making it quite easy to enlarge or reduce the paper size. If we lost you at “square root,” don’t worry about math. The reason the square root of 2 is such a great standard is because you don’t even need to think about it when moving between sizes! By folding a piece of paper in half with the crease parallel to the shortest side you will create the next size down. In this way, A5 is half the size of A4, B6 is half the size of B5 and so on.

All ISO 216 paper sizes have a name that consists of a letter followed by a number. The larger the number, the smaller the paper. The B paper sizes are a bit larger than their A counterparts and are based on the geometric mean of two consecutive A series sheets. For example, B4 is between A3 and A4 in size, and B5 is between A4 and A5.

You may notice that there are no decimal places in ISO 216 but that we have a format called B6.5. That’s because we designed that size specifically for Paper-Oh notebooks. Let’s just call it the next step in the evolution of ISO 216.