Thats the another huge advantage of the DIN formats, its very easy to calculate the weight if you know the grammage of the paper.

DIN A0 = 1m^2 If the paper has a grammage of 80gr/m^2, that means that one sheet of

• DIN A1 weighs 40gr
• DIN A2 weighs 20gr
• DIN A3 weighs 10gr
• DIN A4 weighs 5gr

That makes it really simple to calculate postage without weiging it.

When we are printing stuff in bulk you can also use a scale to measure the number of pages without counting and it usually has a very small margin of error (good enough for distributing flyers and stuff)