A2

The A2 paper size is part of the A series formats defined in the ISO 216 standard. With dimensions of 420 mm x 594 mm, the A2 sheet has an area of 0.25 square meters, half the area of an A1 sheet. The A2 size was developed as part of the A series based on the aspect ratio of √2, enabling the scales of the paper sizes to neatly fold down.

The origins of A2 date back to the late 18th century in Germany along with the other A series sizes. The √2 aspect ratio was first proposed in a 1786 letter by German scientist Georg Christoph Lichtenberg. This geometric ratio allowed for the creation of the A series with its ability to smoothly scale sizes up and down by folding sheets in half. The A2 format itself was formalized in the early 20th century German standards that led to the international standardization of the A series and A2 in 1975. The A2 size is commonly used today for posters, charts, and large drawings. It also serves as a starting point to make booklets and other materials in smaller sizes like A4 when folded in half.