How to calculate what is the weight of A4 paper sheet ?

How can I calculate what is the weight of single A4 paper sheet ? The official grammage of paper is 80 grams per square meter.

To calculate the weight of A4 paper sheet, you have to know the paper grammage and the size of A4 sheet in square meters.

The grammage of paper is in this case 80 grams per 1 square meter.

The dimensions of A4 paper are 29,7 x 21 centimeters, so 0,297 x 0,210 = 0,06237 square meter.

The weight of one A4 paper sheet is 80 x 0,06237 = 4,9896 grams.

Thank you. Can be the paper with grammage 80 grams per square meter, considered as commonly used paper ?

It can be considered as the commonly used paper. Standard office copy paper usually has grammage 80 grams per square meter.