ISO 216 specifies international standard (ISO) paper sizes, used in most countries in the world today. It is the standard which defines the well-known A4 paper size. A millimetre (American spelling: millimeter), symbol mm is an SI unit of length that is equal to one thousandth of a metre. ... The International Organization for Standardization (ISO) is an international standard-setting body composed of representatives from national standards bodies. ... Comparison of the most common paper sizes. ...

A comparison of different A paper sizes

The standard was originally adopted by DIN (as DIN 476) in Germany in 1922, although some of the formats contained therein were independently invented in France during its revolution and later forgotten. Image File history File links A_size_illustration. ... Image File history File links A_size_illustration. ... Deutsches Institut für Normung e. ...

ISO 216 defines two series of paper sizes: A and B. There is also a C series for envelopes, defined in ISO 269. International standard sizes International standard ISO 269 defines several standard envelope sizes, which are designed for use with ISO 216 standard paper sizes: The German standard DIN 678 defines a similar list of envelope formats. ...

A series

Paper in the A series format has a 1:√2 aspect ratio, though this is rounded to the nearest millimetre. A0 is defined so that it has an area of 1 m², prior to the above mentioned rounding. Successive paper sizes in the series A1, A2, A3, etc., are defined by halving the preceding paper size parallel to its shorter side, again prior to rounding. The most frequently used paper size is A4 (210 × 297 mm). A square metre (US spelling: square meter) is by definition the area enclosed by a square with sides each 1 metre long. ...

B series

The B series formats are geometric means between the A series format with the same number and the A series format with one lower number. For example, B1 is a geometric mean between A1 and A0. The sides of B0 are 1 m to √2 m. The geometric mean of a set of positive data is defined as the nth root of the product of all the members of the set, where n is the number of members. ...

There is also an incompatible Japanese B series defined by the JIS. The lengths of JIS B series paper are approximately 1.22 times those of A-series paper. Japanese Industrial Standards (JIS) specifies the standards used for industrial activities in Japan. ...

C series

The C series formats are geometric means between the B series format with the same number and the A series format with the same number, e.g. C2 is the geometric mean between B2 and A2. The C series formats are used mainly for envelopes. An A4 page will fit into a C4 envelope. If you fold the A4 page so that it is A5 in size, it will fit in a C5 envelope and so on.

Application

Prior to the adoption of ISO 216, many different paper formats were used internationally. These formats did not fit into a coherent system and were defined in terms of non-metric units. The ISO 216 formats are organized around the ratio 1:√2; two sheets next to each other together have the same ratio, sideways. This simplifies copying two A4 sheets in reduced size on one, and copying an A4 sheet in magnified size on an A3 sheet or copying half an A4 sheet in magnified size on an A4 sheet. The principal countries not generally using the ISO paper sizes are the United States of America and Canada, which use the Letter, Legal, and Executive system. (Canada uses a P-series of sizes, which are the American paper sizes rounded to metric dimensions.) Comparison of the most common paper sizes. ... Comparison of the most common paper sizes. ...

Rectangular sheets of paper with the ratio 1:√2 are popular in paper folding, where they are sometimes called "A4 rectangles" or "silver rectangles".[1] (Confusingly, "silver rectangle" can also refer to a rectangle in the proportion 1:(1+√2), known as the silver ratio.) In geometry, a rectangle is defined as a quadrilateral polygon in which all four angles are right angles. ... Paper folding is the art of folding paper; it is known in many societies that use paper. ... The factual accuracy of this article is disputed. ...

External links

• International standard paper sizes: ISO 216 details and rationale