Grams per square metre (gsm)
Grams per square metre is the metric system's unit of paper weight — the mass in grams of one square metre of paper. Unlike basis weight, gsm is the same unit across all grades, making cross-grade comparison straightforward.
Gsm sidesteps the parent-sheet complexity of basis weight. It does not matter what kind of paper you are weighing; one square metre of any paper has a measurable mass, and that mass is the gsm value.
Cross-converting between gsm and basis weight requires knowing the parent sheet for the grade family. For bond papers, multiply basis weight by about 3.76 to get gsm; for cover stocks, multiply by about 2.7; for index, by about 1.81. Conversion tables are widely published.
Common gsm ranges: 75-90 for office copy paper, 80-100 for newsprint, 130-300 for linerboard, 200-300 for cardstock and folder weights. International documents (and increasingly U.S. ones) report gsm rather than basis weight.
Related terms
- Basis weightBasis weight is the standard measure of paper weight in the U.S., expressed in pounds per 3,000 square feet of a grade's parent sheet. Elsewhere it is reported as grams per square metre (gsm).
- Caliper (paper)Caliper is the measure of a paper or board's thickness, typically expressed in thousandths of an inch (points or 'pt') in North America and in micrometres elsewhere. A 12-point board is 0.012 inches thick.
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