A4 paper is defined by ISO 2 16, and its specification is 21* 29.7 cm (210 mm× 297 mm). Most countries in the world use this international standard for paper size.

This standard was first incorporated into DIN (DIN 476) in 1922 by Weimar * * and China. Although some formats were developed in France at the same time, they were later forgotten.

ф o 216defines three groups of paper sizes: a, b and c: Group C paper size is mainly used for envelopes.

The aspect ratio of group A paper size is √ 2: 1, and then the nearest millimeter value is rounded. A0 is defined as paper with an area of one square meter and an aspect ratio of √ 2: 1.

The following paper sizes, such as A 1, A2, A3, etc. , are defined as the paper with one digit missing is folded in half along the long side and then discarded to the nearest millimeter value.

The size of group B paper is the geometric average of the same number of sheets and one less number of sheets of group A paper. Before the popularization of printers, group B paper was mostly used. Group C paper size is mainly used for envelopes.

People's Republic of China (PRC) national standard GB/T 148- 1997 "Paper size for printing, writing and drawing" is not equivalent to ISO2 16: 1975.

Extended data:

Dimensional tolerance of A4 paper:

The tolerances specified in ISO 2 16 are used to produce series papers with the following dimensions: (Note: 1 inch =25.4 mm)

1, 1.5 mm (0.06 inch) size can reach 150 mm (5.9 inch),

The length of 2.2 mm (0.08 inch) ranges from 150 to 600 mm (5.9 to 23.6 inch).

3.3 mm (0. 12 inch) Any size exceeding 600 mm (23.6 inch).

Baidu encyclopedia _A4 paper