UK paper sizes

UK Paper Sizes: A Handy Reference

UK paper sizes

One of the things even print industry veterans find themselves doing is looking up paper sizes every so often. It’s easy to forget dimensions, particularly for seldomly used sizes, so we thought we’d publish a ready-reference for our customers and readers — and for ourselves come to think of it! We’ll include the more widely-used UK paper sizes but will leave out those which are more rarefied including ‘old school’ Imperial sizes and US sizes, apart from a few exceptions which we do occasionally see so will mention. There are also a few ‘I didn’t know that‘ moments so do read on …

There are several paper size standards used widely in the UK. The one most commonly used is the ISO ‘A’ series which includes sizes like A5, A4, A3, etc.

ISO ‘A’ paper sizes:

The ‘A’ series of papers sizes is designed in such a way that each step (e.g. from A4 to A3) uses exactly twice the area of the smaller size. So, for example, A3 can be divided up into two A4 sheets whilst A2 can be folded in half to form a folded size of A3, and so on. Here is the official list:

A0    841mm x H1189mm (note that A0 is exactly 1m² in area*)
A1    594mm x 841mm
A2    420mm x 594mm
A3    297mm x 420mm
A4    210mm x 297mm
A5    148mm x 210mm
A6    105mm x 148mm
A7    74mm x 105mm
A8    52mm x 74mm

Sizes beyond A0 were not part of the original ISO specification but have been appended to the system in more recent times. Twice A0 is known as 2A0 (1189 x 1682mm); four times the size of A0 being known as 4A0 (1682 x 2378mm).

* Did you know …

The proportions of the sides of ‘A’ sized sheets are based upon a ratio of 1 to the square root of 2 (which is 1.414, in case you were wondering). They’re designed in this way so that the proportions make scaling from one sheet size to the next really easy — twice A4 is exactly A3, and so on.

However the ‘A’ series also ‘secretly’ embeds a weight metric into its system, thereby allowing the weight of commercial paper stacks – or printed literature requiring posting – to be easily computed, without scales! This is because the A0 size was deliberately designed to have an area of exactly 1 square metre. But how does that help? Well, paper is usually specified in ‘grams per square metre’ (you may have noticed this even when buying simple copier paper) so if one is dealing with, say, 100 sheets of A1 paper and the weight of the paper is 150gsm (150 grams per square metre), one knows that each sheet weighs half of that amount (because it’s half the size of A0). So the computation would be 100 x 75g thereby giving the paper stack a weight of 7,500 grams (exactly 7.5kg). Not useful to end users, perhaps, but incredibly useful to commercial printers who need to be able to estimate consignment weights and the associated shipping/posting costs, even as early as quotation stage.

ISO ‘B’ paper sizes:

‘B’ sheet sizes are based on a very similar principle to the ‘A’ sizes, also having a width to length ratio of 1:1.414 (again, the 1.414 element being the square root of 2). However, instead of the largest size being set in such a way that it has an area of exactly 1m² (as is the case at A0) the largest sheet size in the ‘B’ series (B0) has its shortest side with a length of 1m.

Like with the ‘A’ sizes, each sheet can be divided into 2 to get to the next smallest size (so B0 cut or folded in half through its longest side gives you B1. If you fold it again it gives you B2 and so on). Here is a list of the most common ‘B’ sizes:

B0    1000mm x 1414mm
B1    707mm x 1000mm
B2    500mm x 707mm
B3    353mm x 500mm
B4    250mm x 353mm
B5    176mm x 250mm
B6    125mm x 176mm
B7    88mm x 125mm
B8    62mm x 88mm

It should be noted that ‘B’ sizes are not commonly used by end users and are mostly used by commercial printers who, for the right job, might use them instead of the ‘RA’ or ‘SRA’ paper sizes (see below) and then cut down to a smaller size once printed, for handover to the client.

There is also a size known as ‘Super-B‘ and this is commonly used as a very ‘oversize A3’ sheet in desktop printers like modern inkjets and also within the photographic industry. Super-B is a size of 330mm x 483mm and is also sometimes known as ‘A3+‘. It is not officially part of the ISO ‘B’ series.

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