Minuteman Press in Arlington Texas has a great page to help unravel the weird system of U.S. paper weights (like 8.5″x11″ 24lb bond paper). It turns out that the weight, expressed in pounds, is for 500 sheets (a full ream)–not of the size of paper you are buying–but of the “parent sheet” that the paper is cut down from. In the case of 24lb copy paper, the parent sheet is 22″x17″–so 24lbs refers to the weight of 500 22″x17″ sheets. Other types of paper, like cover stock, have a different size “parent sheet” so you can’t directly compare weights unless you know the size of the parent sheet…Minuteman has some charts to get you started.
The Europeans use just one measurement–”gsm” (grams per square meter)–so you can always directly compare paper weights to one another without tables and calculators.
