Size Guide - 'A' Series Paper sizes
The international paper size standard, based on the German DIN standard for paper sizes.
A0 posters are 841mm x 1,189mm. or 33.1" x 46.8"
A1 posters are 594mm x 841mm. or 23.4" x 33.1"
A2 posters are 420mm x 594mm. or 16.5" x 23.4"
A3 posters are 297mm x 420mm. or 11.7" x 16.5"
A4 posters are 210mm x 297mm. or 8.3" x 11.7"
All of these paper sizes are related to one another - Successive paper sizes in the series A1, A2, A3, and so forth, are defined by halving the preceding paper size along the larger dimension and rounding down. (Technically speaking they all based on a single aspect ratio of square root of 2, or approximately 1:1.4142)