The ISO standard is the most common paper size system used in Europe. The height to width ratio is equivalent to the square root of 2. This means that each size, when cut in half, makes two of the smaller size.
A0 measures one square meter. Common paper types in the A series are:
- A3 (used for tabloid sized newspapers)
- A4 (used for letters, and for printing journals and newsletters)
- A5 (used for notepads and small books).
There are also B series and C series sizes that complement the A series. Printers also have access to the RA and SRA series which allow for trim and bleed when printing. This is useful to know if you are using a book binding company abroad.