## A Handy Guide to UK Paper Sizes

Paper sizes are something even seasoned print veterans find themselves looking up occasionally. While some paper sizes are used on a daily basis at printers and design studios, there are others that are only used a handful of times a year. Those tend to be the sizes most easily forgotten, so we’ve come up with this handy reference guide that can be referred to any time, 365 days of the year. Don’t forget to bookmark it!

The following is not an exhaustive list of paper sizes, but it should cover the most commonly used sizes used by designers and printers around the UK. For the sake of brevity, we’ll leave out the more rarefied ‘legacy’ sizes that we simply tend not to encounter any more.

### ISO Paper Sizes:

You may not have heard of ‘ISO’ paper sizes, but you will have used sizes like A4 and A3 perhaps on a weekly basis. A4, A3, A5, A2, B4 and B5 are probably the most easily recognisable examples of ISO ‘A’ and ISO ‘B’ paper sizes.

ISO sizes have several neat, and very handy, mathematical properties about them:

• The ratio of their sides is always 1 to 1.414 (the square root of 2, by the way).
• To mentally compute the dimensions from one ISO paper size to the next, you simply keep the longest side and double the shortest. So A4 (210mm x 297mm) becomes A3 (297mm x 420mm). We simply doubled the shortest side (210mm) to get that new 420mm dimension, but kept the existing 267mm dimension — easy!
• Note that the physical paper size at each step up is DOUBLE the paper area. So A4 is half the size of A3 (fold A3 in half and you end up with A4 again). A3 is in turn half the physical size of A2 and so on.
• You can alternatively enlarge to the next ISO size (e.g. from A4 to A3) by enlarging the original 1.414 times. So, on a photocopier, for example, you would set the magnification to 141.4%.
• Most ingeniously, the ISO ‘A’ sizes are designed to allow printers to easily compute the weight of a printed stack of papers simply by counting the sheets. It’s based on the fact that the size A0 is exactly 1 square metre in area. So, if you know you have paper that’s, say, 150gsm in weight (paper is specified in grams per square metre; gsm), you know that a stack of one hundred A0 sheets will be 100 x 150gsm, which is 15000grams (i.e. 1.5kg in weight). If your stack happened to be A1, then you simply need to divide that by two (because, as we learned above, the next A size down is half the size). For A2 you halve it again and so on.

### ISO ‘A’ sizes:

The ISO ‘A’ series of paper sizes is most widely used for printing and design in the UK; most people will use A4 paper, for example, on a daily basis. As we mentioned above, each ‘step’ down from one A size to the next is exactly half the size, as you can see in the diagram above/right. Here are the main A sizes:

• A0 = 841mm x H1189mm
• 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
• A9 = 37mm x 52mm

If you want to go larger than A0, the next size up is called “2A0” (1189 x 1682mm). Use the maths trick above to go up from there to 3A0, 4A0 and beyond.

### ISO ‘B’ paper sizes:

Exactly as with the ‘A’ sizes, each ‘B’ paper size can be Read more