A sizes are part of the ISO 216 standard which are used internationally to determine paper sizes, there are a few exceptions to this however. North America and parts of Central and South America use North America paper sizes such as "Letter" and "Legal", which are also based on the imperial measurement system. We have made it easy to convert the A sizes into millimetres and inches using the table below.
You can work out the sizing of paper in A sizes yourself, double the length of the sides to determine the length of the sides next size up i.e. to find the measurements of A3 from A4 (210mm x 297mm) -> (210 times 2 = 420) and (297 times 2 = 594), A3 size would therefore be 420 x 594mm.
| Size | Metric (mm) | Imperial (inch) |
| A0 | 841 x 1189 mm | 33.1 x 46.8 in |
| A1 | 594 x 841 mm | 23.4 x 33.1 in |
| A2 | 420 x 594 mm | 16.5 x 23.4 in |
| A3 | 297 x 420 mm | 11.7 x 16.5 in |
| A4 | 210 x 297 mm | 8.3 x 11.7 in |
| A5 | 148 x 210 mm | 5.8 x 8.3 in |
| A6 | 105 x 148 mm | 4.1 5.8 in |
| A7 | 74 x 105 mm | 2.9 x 4.1 in |
| A8 | 52 x 74 mm | 2.0 x 2.9 in |
| A9 | 37 x 52 mm | 1.5 x 2.0 in |
| A10 | 26 x 37 mm | 1.0 x 1.5 in |
In design print measurements are worked out width x height, this is the same as x and y coordinates of a graph. The image below shows some of the A paper sizes and how they relate to the adjoining size, you will notice that half the longest side matches the length of the previous A size's shortest side.
There are A sizes larger than A0, these are indicated with a multiple of 2 before A0. For example the size size up would be 2A0, then 4A0, etc. These larger sizes however are not included in the ISO 216 standard but have developed to allow for larger paper sizes that have since become more common.
In the paper industry ISO 216 specifies tolerances for the production of A series paper sizes, which are as follows: ±1.5 mm (0.06 in) for dimensions up to 150 mm (5.9 in) ±2 mm (0.08 in) for lengths in the range 150 to 600 mm (5.9 to 23.6 in). This is important for framing as they should always been an allowance made so that the prints can fit within the frame and not be too loose/too tight.