ISO 216: Paper Sizes, Read Aloud

This episode reads the Wikipedia article on ISO 216 in its own order. ISO 216 is the international standard for paper sizes. A short gloss follows each section. It says what the section governs, what it assumes, how other countries do it, and when it changed. The ISO text itself is summarised from Wikipedia and is not read word for word.

ISO 216

The standard defines the A, B and C series of paper sizes. It is used everywhere except North America, the Philippines and parts of Latin America. Every size has the aspect ratio of the square root of two to one. A sheet in that ratio, cut or folded in half widthways, gives two halves with the same ratio. Each size has half the area of the next larger size in its series.

Dimensions of A, B and C series

The article gives one table in millimetres and inches. It runs from 4A0, at 1682 by 2378 mm, down to A10, at 26 by 37 mm. A4 measures 210 by 297 mm. B0 measures 1000 by 1414 mm, and C0 measures 917 by 1297 mm.

History

The earliest known mention of the ratio is in a letter from Georg Christoph Lichtenberg, dated 25 October 1786. A French law of 1798 listed early forms of A2, A3, B3, B4 and B5. Wilhelm Ostwald proposed a world format in 1911. Walter Porstmann argued in 1918 that the system should rest on area. The German standard DIN 476 followed. This article dates it to 1921, and the article on paper size dates it to 18 August 1922. It became ISO 216 and the United Nations document format in 1975.

Advantages

A sheet halves into two sheets of the next size, so A4 folds into an A5 brochure. A copier can reduce A4 to A5 or enlarge A4 to A3. Weight is easy to work out as well. An A4 sheet of 80 g/m² paper weighs 5 g.

Properties

A0 has an area of one square metre before rounding. The B series sits at the geometric means between A sizes, and the shorter side of B0 is exactly one metre. The C series sits between B and A, and it is used mainly for envelopes. An unfolded A4 page fits a C4 envelope.

Tolerances

The allowed tolerance is ±1.5 mm up to 150 mm, ±2.0 mm from 150 to 600 mm, and ±3.0 mm above 600 mm. The older DIN 476 allowed less.

Application

The United States and Canada use North American sizes. Letter, 8.5 by 11 inches, has an aspect ratio of 22 to 17. Several Latin American countries adopted ISO 216 officially but still mostly use US sizes.

Matching technical pen widths

The pen widths in ISO 9175-1 also step up by the square root of two. Each width has its own colour code.

Overformats

DIN 476 lists 2A0 and 4A0. ISO 216:2007 says these rarely used sizes also belong to the series.

Sources