The answer depends on a few variables:

1) The size of the paper

2) The thickness of the paper

3) The type of the paper

Paper is measures in a weight called GSM (Grams Per Square Meter) so when buying paper you will see weights of 80 GSM, 100 GSM or 120 GSM. You can buy paper is all different GSM's depending on what you need it for. If you are printing lots of ink onto the paper you will need a higher GSM weight as the paper will get clogged up and the paint will not be very presentable.

Obviously you need better quality paper as well as thicker paper if you are printing heavy ink onto the paper to cope with the quality of the print.

The average size paper is "A4" in the UK and the average thickness is 80 GSM paper.

If the paper is half the thickness I.E. 80 gsms then the weight would be 40 GSM's.

Certain paper such as A1 or A0 artwork type paper or post paper will be a thicker material so the answer will be a lot heavier.

Paper today can be made of many different materils from a plastic coating, to thin fibre coating and the threads can be made up of different material and glue to hold them together. This will all effect the weight of paper.