Sometimes, when working with graphics, it may be of hand to know the ISO definition for the different paper format. Here is a nice explanation with a comprehensive table.

A0 841 × 1189

A1 594 × 841

A2 420 × 594

A3 297 × 420

A4 210 × 297

A5 148 × 210

A6 105 × 148

A7 74 × 105

A8 52 × 74

A9 37 × 52

A10 26 × 37