There are a few ways the paper industry measures paper weights. Here are the most common:
M Weight: The weight of 1000 qty. sheets of any particular paper.
Basis Weight: The weight of 500 qty. sheets in its basic size. Please be aware that different paper categories have different paper basic sizes.
Caliper: This indicates a paper’s thickness measures in thousandths of an inch. A paper’s caliper may be listed as .010 or 10 point. The greater the caliper (thickness of the paper), the greater the paper weight.
GSM: The metric system measures paper weight in grams per square meter. All categories of paper use this scale.