A4 is a standard paper size, defined by the international standard ISO 216 as 210×297 mm (roughly 8.27×11.69 in). It is the normal size of paper for both domestic and business purposes in all countries except the United States, Canada, Mexico, the Philippines, Chile and some other American countries. See paper size standards in North America.

The illustration shows that A4 has half the area of A3 and twice the area of A5. The A series of paper sizes is based on A0 which has an area of 1 square meter and a length to width ratio of √2 (the square root of 2 ≈ 1.414). This ratio produces the ISO 216 range with each size having half the area of the previous size.

In countries that do not use ISO 216 paper sizes as standard, A4 paper is sometimes available in small quantity; office equipment meant to be sold in such countries is sometimes built to accommodate both A4 and US letter size paper.

See also

• Paper size
• Deutsches Institut für Normung (German Institute for Standardization)
• International Organisation for Standardisation

External links

• A thorough explanation of ISO paper sizes

ISO standards | Stationery

A4-papir | A4 | DIN A4 | A4 | A4 (papierformaat) | A4 (tamanho de papel)