Standard Paper Sizes – ISO and ANSI Formats

Stack of papers that conform to the standard paper sizes ANSI ISO A A4

Most people are unlikely to contemplate the systems in place that prevent a jagged stack of paper of varying lengths and sizes. Certainly, since the proliferation of and dependence on technological devices, this question seems insignificant to our daily lives. However, while digital media has dominated lifestyles, paper is still crucial to completing a host of daily tasks, and the standard sizes of these cellulose sheets derive from organizations active in the standards community.

Worldwide, the most common paper sizes are of the ISO-A format. This name, of course, derives from its specifications for being laid out in ISO 216, an international standard developed and published by the International Organization for Standardization (ISO).

What Is ISO A4?

The common ISO A4 paper for office documents has was conceived long ago, likely being created by Georg Christoph Lichtenberg as a letter to Johann Beckmann in 1786 detailing the very style on which it was written. Almost one and one half centuries later, Deutsches Institut für Normung (DIN, the German Institute for Standardization) officially standardized paper styles off Lichtenberg’s format in the DIN A4 standard.

As time pressed forward, the standard usage of DIN A4 paper types spread from their initial use in Germany and Austria and into some other European nations. After World War II came and passed, the standard found usage in dozens of countries. In response, ISO established the styles as part of the ISO 216 standard in 1975.

How Do the ISO Standard Paper Formats Scale?

The ISO-A paper style series follows the halving, similarity, and proportionality principles. The simplest way to understand how these work is that A4 is half the size of A3, which is, in turn, half the size of A2, and so on to A0, which is the largest in the range at exactly 1 square meter of paper.

In terms of scaling, this presents a distinct advantage. If a sheet with an aspect ratio of the square root of 2 is divided into two equal halves parallel to its shortest sides, then the halves will retain the √2 aspect ratio. This grants the ability to scale without compromising the aspect ratio. Interestingly, Lichtenberg mentioned this same idea in his 1786 letter.

ISO 216, the current version of which is ISO 216:2007 – Writing paper and certain classes of printed matter – Trimmed sizes – A and B series, and indication of machine direction, also established the ISO-B series of paper sizes. These follow the same principles as the A series, but they are obtained by placing the geometrical means between adjacent sides of the A series in sequence. ISO-B paper sizes are often used for posters.

Stacks of paper that conform to ANSI A ISO A4

There are also ISO C paper sizes, which are used for envelopes to match the A series paper and were established by ISO 269.

What Is the Standard Letter Format?

ISO A4 is nearly universal as the standard letter format, but it has yet to be adopted by two countries—the United States and Canada.

The origin of the North American paper size standard known as letter paper is relatively indiscernible, but the paper size—at 8.5”x11”—became a recognized standard in 1921 to reduce waste in industry. However, it didn’t become the national standard size of the US government until the early 1980s. A little after this time, in 1992, the first edition of ANSI/ASME Y14.1 was published. This standard, developed by the American Society of Mechanical Engineers (ASME), fully standardized the American paper sizes.

ANSI A was modeled off letter paper, while ANSI B comes in two forms: ledger and tabloid, at 11”x17” and 17”x11”, respectively. The larger sizes on this system are ANSI C, ANSI D, and ANSI E. The ANSI paper sizes are somewhat similar to the ISO sizes, in that cutting the sheet in half would produce two sheets of the next smaller size.

About ANSI/ASME Y14.1

ANSI/ASME Y14.1 was revised several times, and it is currently ASME Y14.1-2020: Decimal Inch Drawing Sheet Size and Format. ASME Y14.1M-2012: Metric Drawing Sheet Size and Format alternatively makes use of the ISO-A format. Despite the official adoption of the ISO standard, several nations still use the ANSI A, or US letter, format.

How Do the ANSI and ISO Standard Paper Formats Relate?

The existence of both the ANSI and ISO formats, similar to the standard variations we have seen with other industries and products, functions relatively seamlessly. In fact, the two primary sizes of letter paper, ANSI A and ISO A4, are incredibly close in size, at 8.5”x11” and 8.27”x11.69”, respectively.

Please note that architectural sizes vary from these standard paper sizes. These are known as Architectural (ARCH) A, B, C, D, E1, and E.

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