The most commonly used paper size is A4, A4 is 210mm x 297mm

Standard paper Sizes A0, A1, A2, A3, A4, A5, A6

To work out other paper sizes just remember the size of A4.
Standard paper sizes are really easy to work out all you do is half the longest edge to get the next size down, and to go up double the shortest edge
For example:  A4 is 210 x 297mm. Half of 297mm is 148mm.
Therefore A5 is 210 x 148mm.  
A3 is 420mm x 297mm, double 210 = 420

It's that simple

We stock all standard paper sizes and types.
Obviously A4 is the most common, but if you need any other type we will source it and deliver it to you.
We also do printing on all paper sizes including A1 Poster printing.