Everyone is familiar with the most common of paper sizes, A4, but not everyone knows where the term comes from or what it means. As you work through the sizes, each one is half the size of the one before. Paper in the ‘A’ range is calculated from A0, which is not one most people ever come across, having an area of one square metre. The proportions of all ‘A’ paper is not the easiest maths; the length divided by the width gives an answer of 1.4142, which is why the actual dimensions of the paper do not correspond to any round figure in metric or imperial.
From A0, we get A1, which is the size of some of the bigger flip charts; this is half the size of A0. A2 is also often used as a flip chart, and is easier to picture, being twice the size of a piece of A3, or approximately a tabloid newspaper opened out. Next comes A3, most usually seen as posters for amateur dramatics, flower shows, public events, etc. Some high-end home printers now take A3, but it is an easy job to enlarge the commonest of all, A4, into the twice-as-large A3 at a high street print centre.
Most artwork printed on A4 will enlarge quite nicely to A3 without loss of quality. A5 is the next size down and is approximately the size of a greetings card; halve it again and you get a notelet, A6. A7 is a playing card, more or less and A8 is a smallish business card.
C is the designation given to envelopes to hold paper of the A sizes and is very simple. An envelope of size C4 will hold a piece of A4 paper; a C5 will hold either a piece of A4 folded in half, or a piece of unfolded A5, and so on. This makes stationery ordering simple and waste free.
Click on the link for more information on paper sizes.