The base A0 size of paper is defined as having an area of 1 m2. Rounded to the nearest millimetre, the A0 paper size is 841 by 1,189 millimetres (33.1 in × 46.8 in).
Successive paper sizes in the series A1, A2, A3, and so forth, are defined by halving the preceding paper size across the larger dimension. This also effectively halves the area of each sheet. The most frequently used paper size is A4 measuring 210 by 297 millimetres (8.27 in × 11.7 in).
In addition to the A series, there is a less common B series. The area of B series sheets is the geometric mean of successive A series sheets. So, B1 is between A0 and A1 in size, with an area of 0.707 m2 (1⁄√2 m2). As a result, B0 is 1 metre wide, and other sizes in the B series are a half, a quarter or further fractions of a metre wide. While less common in office use, it is used for a variety of special situations. Many posters use B-series paper or a close approximation, such as 50 cm × 70 cm; B5 is a relatively common choice for books. The B series is also used for envelopes and passports. The B-series is widely used in the printing industry to describe both paper sizes and printing press sizes, including digital presses. B3 paper is used to print two US letter or A4 pages side by side using imposition; four pages would be printed on B2, eight on B1, etc.
The C series is usually used for envelopes and is defined in ISO 269. The area of C series sheets is the geometric mean of the areas of the A and B series sheets of the same number; for instance, the area of a C4 sheet is the geometric mean of the areas of an A4 sheet and a B4 sheet. This means that C4 is slightly larger than A4, and slightly smaller than B4. The practical usage of this is that a letter written on A4 paper fits inside a C4 envelope, and C4 paper fits inside a B4 envelope.
North American Sizes
The United States, Canada and Mexico use a different system of paper sizes compared to the rest of the world. The current standard sizes are unique to that continent, although due to the size of the North American market and proliferation of both software and printing hardware from the region, other parts of the world have become increasingly familiar with these sizes (though not necessarily the paper itself). The traditional North American inch-based sizes differ from those described below. “Letter”, “legal”, and “ledger”/”tabloid” are by far the most commonly used of these for everyday activities. The origins of the exact dimensions of “letter” size paper (8 1⁄2 in × 11 in or 215.9 mm × 279.4 mm) are lost in tradition and not well documented. The American Forest and Paper Association argues that the dimension originates from the days of manual paper making, and that the 11-inch length of the page is about a quarter of “the average maximum stretch of an experienced vatman’s arms.” However, this does not explain the width or aspect ratio. Outside of North America, Letter size may also be known as “American Quarto” and the size is indeed almost exactly one quarter of the old Imperial (British) paper size known as “demy quarto” (17 1⁄2 × 22 1⁄2 in), allowing 1⁄2 inch for trimming.
|Size||in × in||mm × mm||Similar Canadian P size|
|Letter||8 1⁄2 × 11||215.9 × 279.4||P4: 215 × 280|
|Government-Letter||8 × 10 1⁄2||203.2 × 266.7|
|Legal||8 1⁄2 × 14||215.9 × 355.6|
|Junior Legal||8 × 5||203.2 × 127|
|Ledger||17 × 11||432 × 279|
|Tabloid||11 × 17||279 × 432|
In addition to the ANSI system as listed above, there is a corresponding series of paper sizes used for architectural purposes. This series also shares the property that bisecting each size produces two of the size below, with alternating aspect ratios. It may be preferred by North American architects because the aspect ratios (4:3 and 3:2) are ratios of small integers, unlike their ANSI (or ISO) counterparts. Furthermore, the aspect ratio 4:3 matches the traditional aspect ratio for computer displays. The architectural series, usually abbreviated “Arch”, is shown below:
|Name||in × in||mm × mm||Ratio|
|Arch A||9 × 12||229 × 305||3:4|
|Arch B||12 × 18||305 × 457||2:3|
|Arch C||18 × 24||457 × 610||3:4|
|Arch D||24 × 36||610 × 914||2:3|
|Arch E||36 × 48||914 × 1219||3:4|
|Arch E1||30 × 42||762 × 1067||5:7|
|Arch E2||26 × 38||660 × 965||13:19|
|Arch E3||27 × 39||686 × 991||9:13|
Paper Sizes | A4 Sizes | Letters Sizes | Legal Sizes | Larger Sizes