A Guide to Paper Sizes

What size is A4 paper? And A3 and A5 and A0 for that matter! The most common paper sizes used in the UK for printing and stationery are named using the letter A, also known as International Paper Sizes. The range begins with tiny A10 (37mm x 26mm) and goes all the way through to the mighty A0 (1189mm x 841mm).

With A sized paper, however many times you double the short edge or half the long edge, it will always have the same width to height ratio. For example, the dimensions of A4 paper are 210x297mm, and half of A4 equals A5, and double A4 equals A3.

Starting from A0, all subsequent A paper sizes are determined by halving the paper on its longest size. A0 halves to become A1, which halves to become A2, all the way down to A10. Remember, the length of the smaller size is always equal to the width of the larger size. For example, the length of A4 is 297mm which is also the width of A3.

To many people wordwide, excluding North America and Canada, the most familiar paper size size is A4 (a familiar 210mm x 297mm). It is commonly used for letters and correspondence in the UK and it is the standard paper size for most home printers. I bet you’ve seen, used and/or scribbled on at least one piece of this today!

At Printroom Group we print on sizes from A5 to A0, both unbound and with various binding types (as well as custom size printing if that’s what you’re looking for).