A10

The A10 paper size is the smallest format currently defined in the A series within the ISO 216 standard. With tiny dimensions of 26 mm x 37 mm, the A10 sheet has an miniscule area of 0.0009765625 square meters. The A10 size was established as part of the A series based on the aspect ratio of √2, enabling each size to neatly fold down from the larger sheets.

The origins of A10 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 extremely small A10 format was formalized in the early 20th century German standards that led to its inclusion in the ISO 216 standard published in 1975. The remarkably compact A10 is well-suited for tiny labels, stamps, and micro booklets. Its minuscule dimensions allow multiple A10 pages to fit within larger A sizes.