The basis weight of paper stated in metric terms of grammes per square metre and expressed as g/m2. Thus a sheet of paper 17 x 22 with a basis weight of 20 lbs. For 500 sheets would be expressed metrically as 75 g/m2. To convert from basis weight to grammes per square metre (g/m2), multiply basis weight by 1406. 5 (a constant factor) and divide by the number of square inches in base sheet.