what is a4 paper size

A4 paper size is a standard paper size used in most countries around the world, except for the United States, Canada, and some parts of Mexico. A piece of A4 paper measures 21 x 29.7 cm or 210 x 297 mm. It is part of the A-series paper sizes, which are defined by the ISO 216 standard. The A-series paper sizes are based on a system where each size is half the size of the previous one, starting from A0, which has an area of one square meter. A4 paper is commonly used for everyday printing and stationery in the UK and other countries that follow the ISO 216 standard.