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.

ISO ‘C’ sizes … are for envelopes:

‘C’ paper sizes are primarily there to be used for envelopes which will suit the ‘A’ series of paper sizes. For example, a C6 envelope will suit an A6 postcard while a C5 envelope will suit an A5 postcard (or A4 sheet folded in half to A5). As one might expect in view of that, the width to length proportions also equate to (approx.) 1:1.414. Here are the most commonly used sizes for the UK.

C3    458mm x 324mm (that’s a BIG envelope!)
C4    324mm x 229mm
C5    229mm x 162mm
C6    162mm x 114mm

‘DL’ (or rather ‘DLE’) envelope size:

There is a standard envelope size which suits an A4 letter folded into 3. The envelope size, known officially as ‘DLE‘ but usually unofficially referred to as ‘DL‘ is sized at 220mm x 110mm so leaves room for some ‘slack’ inside. This significant slack, however, means that the addressee on any enclosed letter has to be very carefully positioned on the document and the letter also needs to be folded very carefully if ‘window’ style envelopes are used. It’s when they’re not that you will sometimes see the postman having to tap the edges of an envelope to shake the address into better view through the envelope window.

In a slight twist, the true size specification for ‘DL’ is exactly one-third A4, being 99mm x 210mm however when you order ‘DL’ envelopes from your printer or stationer pretty much every  commercial supplier in the UK will know that you really expect your envelope to be 220mm x 110mm i.e. ‘DLE’ size rather than true ‘DL’ size.

ISO ‘D’ sizes:

‘D’ sizes are, in theory, suited as envelope sizes for the ‘B’ series of papers (rather like the ‘C’ envelope sizes are to ‘A’ series paper sizes). However in reality ‘D’ sizes are very rarely used in the UK so we will not clutter up this article by including more than this passing reference to them.

‘RA’ and ‘SRA’ series of paper sizes

These are related to the ISO ‘A’ sizes above except they are a larger sheet size for use by printers. Why are they larger? Well, printers need to print beyond the final trimmed edges of the sheet. This allows for the addition or registration marks and trim marks etc. and also avoids unintended white margins where images print to the very edge. Printing more than one copy on an uncut oversize sheet also makes for better economy. Of course, in one of the final printing and finishing processes, the oversize sheets will usually be cut down to a standard ISO ‘A’  size before handover to the customer.

RA0     860mm × 1220mm
RA1     610mm × 860mm
RA2     430mm × 610mm
RA3     305mm × 430mm
RA4     215mm × 305mm

SRA0     900mm × 1280mm
SRA1     640mm × 900mm
SRA2     450mm × 640mm
SRA3     320mm × 450mm
SRA4     225mm × 320mm

Traditional ‘English’ paper sizes

From a general use point of view, many of the ‘old school’ English sizes have all but died out in recent decades. ‘Imperial‘, ‘Half Imperial‘ and ‘Royal‘ are still used a little bit in the UK, but usually only in the art world.

Foolscap‘ (also originally known as ‘Folio‘) is sometimes still referred to but usually only by much older generations. It is also unfortunate that ‘Foolscap’ has widely differing size specifications depending on where you are in the world. From the UK’s point of view its meaning refers to a size not too dissimilar to A4 (although the longest side was 330mm rather than 297mm) however in some other countries Foolscap is around twice that size. So we won’t complicate matters by including such confusing legacy sizes here.

‘International Business Card’ size

As a unique exception to all the size standards above, the most common size for a business card in the UK and internationally is the appropriately-named ‘International Credit Card‘ size (sized as per a plastic credit card so as to easily keep cards in one’s wallet or credit card holder). Strictly speaking the official specification for this size is 53.98mm x 85.6mm although many UK printers tend to round it up/down to 54mm (or 55mm) x 85mm (or less commonly 86mm).

U.S. sizes commonly encountered in the UK

Of the various American sizes in existence, just a couple are regularly encountered in the UK and even then they’re encountered usually by mistake. For example if you are a regular Microsoft Word user you might have accidentally left the default paper size set to the U.S. ‘Letter‘ size which, annoyingly, is less tall but wider than A4, which can cause major layout and desk-top printing problems if the size is not overridden and re-targeted, for example to an A4 sheet size.

Letter     216mm x 279mm
Legal     216mm x 356mm

We hope you have found this reference useful. It was put together by Firstpoint Print which is a printer and print specialist based in London, having three branches (London Bridge, Victoria and Clerkenwell). Contact us for further information or a no-obligation print quotation if you are interested in top quality, competitively-priced, fast turnaround digital, litho or large format printing. We’d be delighted to help and can even supply creative graphic design and artwork.