Here is an image illustrating the standard ISO paper sizes and their relationships.
Paper sizes
Paper sizes may be specified by referring to the ISO (International Standards Organisation) series of paper sizes. The ISO has been responsible for standardising a number of elements common to publishing.
The following are the standard metric paper sizes in common use today ...
- A0 841 x 1189mm
- A1 594 x 841mm
- A2 420 x 594mm
- A3 297 x 420mm
- A4 210 x 297mm
- A5 148 x 210m
- A6 105 x 148mm
There are also SRA sizes which are basically oversize paper sizes allowing for trimming back to the A sizes where images have been laid out to bleed over the edge of a page.