Paper Sizes: Easy As A, B, C?

If you’re involved in the commercial world, it can be very helpful to understand the different regional and international standards that apply to an everyday essential such as paper.

Think of the billions of sheets that pass through copiers and printers each day globally – getting it wrong can cause serious delays and bring work to a halt! What are the different standards in paper sheet sizes and where do they apply?

A numbers game

Many people will have come across the best-known print paper sizes, the “A” series, at some point. Several important rules apply: firstly, the larger the number, the smaller the paper sheet (therefore A0 is the largest, measuring 841 by 1,189 millimetres, while the smallest for most practical purposes, A7, is 74 x 105mm). Each size down represents half the preceding paper size, as measured across the larger dimension. An A3 sheet then, is equal to two A4 sheets, and so on. Scaling is the most important aspect: the sheets have a common aspect ratio of √2, which assists in printing, since the same artwork can be reduced or enlarged and will still fit perfectly. The weights of the different sizes of paper can be calculated readily as well.

Mixing and matching

Professional printers use a slightly larger version of the A series in order to allow for bleed, trimming, cutting and binding. The A series comes under the international standard ISO 216, as does another common paper series, the B series. The B series uses a geometric mean (average) between the various A sizes, so that, for example, B1 is between A0 and A1 in size. Sometimes called poster size, this series is used for envelopes and specialist print runs too. The C series, mostly used for envelopes, comes under ISO 269.

From letters to ledgers

The major global divergence in paper standards is between the A series and the paper sizes used in America, Canada, Mexico and the Philippines (though sometimes here mixed standards apply). Sizes range from letter size (140 x 216mm/5.5 x 8.5in) to ledger size (279 x 432mm/11.0 x 17.0in), with legal and letter sizes representing the closest equivalent to A4.

Finally, the old imperial paper sizes, with their names drawn originally from watermarks such as foolscap, haven’t entirely disappeared. They’re still used by legal and other professionals, though now the paper is designed for modern printers, rather than quill pens!