Metric system equivalent of a paper's basis weight. Basis weight, expressed in pounds, is typically the weight of one ream (500 sheets) of a paper cut to its basic size, which can vary by paper grade. Grammage is defined as the weight (in grams) of a square meter of paper, and is expressed in grams per square meters (g/m2). To convert from a known basis weight and basic size to g/m2:
'Trade Size'g/m2 to lbs.lbs. to g/m2
17 x 220.2663.760
20 x 260.3702.704
24 x 360.6141.627
25 x 380.6751.480
So, to find the grammage of a 20-lb. 17 x 22 bond paper, multiply the basis weight (20 lbs.) by 3.760 to get 75.2 g/m2. Similarly, to find the basis weight of a 103.6 g/m2 book paper, multiply the grammage by the conversion factor corresponding to the basic size of a book paper (25 x 38) to get 103.6 x 0.675 = 69.93, or approximately 70-pound paper.