ISO 216

ISO 216. It is an international standard that specifies the paper sizes used in most countries around the world today, with the notable exceptions of the United States, Canada, and parts of Mexico. The standard, first published in 1975, defines the well-known A series, as well as the B series and C series formats, all based on a consistent mathematical principle. Its widespread adoption facilitates the scaling of documents, printing, and stationery across international borders and within various industries.

Overview

The primary purpose of this specification is to create a rationalized system of paper dimensions that maintains the same aspect ratio when a sheet is folded or cut in half parallel to its shorter sides. This system is rooted in a metric base, with the foundational A0 size defined as having an area of one square metre. The standard is maintained by the ISO/TC 6 technical committee, which oversees standards for paper, board, and pulps. Its implementation simplifies design, filing, and manufacturing processes for a vast range of products, from office paper and envelopes to posters and technical drawings, promoting efficiency and reducing waste.

Dimensions and series

The standard defines three primary series of cut sizes. The A series, the most commonly used, begins with A0 (841 × 1189 mm) and proceeds through A1, A2, A3, A4, A5, and smaller, with each subsequent size being half the area of the previous one. The B series sizes, such as B0 (1000 × 1414 mm), are geometric means between the A series sizes and are often used for books, posters, and passports. The C series, with C4 and C5 being typical examples, is primarily specified for envelopes designed to hold A series sheets without folding; for instance, an A4 sheet fits neatly into a C4 envelope. The consistent √2:1 aspect ratio across all series is a fundamental and elegant feature of the system.

Tolerances and aspect ratio

The standard specifies precise manufacturing tolerances for the dimensions to ensure consistency. For most sizes up to 150 mm, the tolerance is ±1.5 mm, while for dimensions above 150 mm, it is ±2 mm. The crucial aspect ratio of 1:√2 (approximately 1:1.4142) is maintained because when a sheet with this ratio is halved, the resulting halves retain the same ratio. This property is essential for the integrity of the scaling system and is a direct result of the Lichtenberg ratio, named after the German scientist who described its benefits in a 1786 letter. This mathematical consistency is what allows for perfect scaling from A0 down to A10 without distortion.

History and adoption

The geometric principles behind the standard have a long history, with early observations noted by scholars like Georg Christoph Lichtenberg. The system was formally pioneered in the early 20th century by Dr. Walter Porstmann, who successfully advocated for its adoption as the German standard DIN 476 in 1922. Following its success in Germany and later across Europe, it was formally established as an international standard in 1975. Today, it is the dominant paper size system used in every country except the United States and Canada, which primarily use Letter and Legal sizes based on traditional Imperial units. The system's adoption was significantly aided by its inclusion in other standards, such as those for technical drawings.

Related standards

Several other ISO standards are closely associated with or extend the scope of this specification. ISO 217 and ISO 269 define untrimmed raw formats and supplementary envelope sizes, respectively. The ISO 838 standard specifies the two-hole filing system used with A4 sheets. For continuous forms, ISO 2784 applies. The standard also forms the basis for many national standards, such as the JIS P 0138 in Japan, the BS EN ISO 216 in the United Kingdom, and the original DIN 476 in Germany. Its principles influence the design of products ranging from printers and photocopiers to filing cabinets and briefcases worldwide. Category:ISO standards Category:Paper