Guide To... Paper Sizes

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16 November 2020

In this week’s Geek Out, we are debunking a mystery that can confuse any marketeer at first glance – paper sizes. Paper sizing is a key aspect for digital printing, after all, a poster printed on A5 paper will attract significantly less attention than one printed on A2, and all of that gets even more confusing when other measures (such as B sizes and RA’s) are added into the mix.

Learning your ABC’s

ISO 216 is an international standard for paper sizing and is used across the world (except for North America and some parts of Latin America). This standard sets out 3 individual series of paper sizes, A, B, and C.

The most common paper sizes are listed in A-Series Sizes, these are the standard A4s and A3s that we’ve all grown up with and are also the sizes that we here at UKPrinting typically use for our digitally printed products such as Posters and Flyers. Each A Size is half the size of its smaller numbered counterpart, for example an A4 sized sheet measures at 210x297mm, whereas an A3 sized sheet measures 297x420mm, with the width of the larger size becoming the length of the smaller. This aspect ratio is the same across A, B, and C sizes, albeit with slightly different starting sizes.



RA and SRA paper formats are two other series of paper sizes that you may commonly find in printing. These are all measured out based on the A Size format to allow for trims and bleeds on printed materials. RA stands for Raw Format A and is defined as being 105% of the respective A series Size (so RA2 is 430x610mm and opposed to A2 at 420x594mm), this is to account for normal trims. Meanwhile, SRA stands for Supplementary Raw Format A and they are based on 115%  of the standard A size to allow for bleeds and extra trims.


Legal or Tabloid

Standard paper sizes in the US use a different system of sizing with no consistent aspect ratio. Most of these sizes can be measured up against ISO A-Series sizes relatively well (A5 almost measuring up to a Half Letter size, A4 being extremely similar to US Letter size, and A3 being the closest equivalent to Ledger or Tabloid size). There also additional sizes, Legal and Junior Legal which are narrower sizes.