Below we have guides for ISO A Series Paper Sizes and A Strip Paper Sizes. The sizes are in millimetres and will give you a visual explanation of how the sizes relate to each other – for example A5 is half of A4 size paper and A2 is half of A1 size paper.
The ISO system is based on three series:
The full sheet in each series is designated by the number 0. The longer length is then halved to give 1, and halved again to give 2 and halved again to give 3 etc. So, A4 is half of A3, A5 is half of A4 etc.
The A series is based on A0. The size, 841 x 1189, is one square metre in area. The weight of the paper is also based on the weight of one square metre in grammes, i.e. ‘gsm’. When expressing the measurements, care should be taken as traditionally the upright measure was given first and the horizontal measurement second.