ISO A Series Paper Sizes
- A sizes for general printing and stationery.
- B sizes for posters and some larger envelopes.
- C sizes for general envelopes or folders to contain A sizes.
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
The weight of the paper is also based on the weight of one square metre in grammes, i.e. ‘gsm’.