• 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’.
 
paper-sizes