International standard paper sizes

Rare card · No. 63125

ISO 216 is an international standard for paper sizes, used around the world except in North America, the Philippines and parts of Latin America. The standard defines the "A", "B" and "C" series of paper sizes, which includes A4, the most commonly available paper size worldwide. Two supplementary standards, ISO 217 and ISO 269, define related paper sizes. All ISO 216, ISO 217 and ISO 269 paper sizes (except some envelopes) have the same aspect ratio, √2:1, within rounding error. This ratio has the unique property that when cut or folded in half widthways, the halves also have the same aspect ratio. Each ISO paper size is one half of the area of the next larger size in the same series.

Read on Wikipedia · Image S. Wetzel (Das Papierformat DIN A4), CC BY-SA 4.0