How much a ream of paper weighs depends on the thickness of the sheets. A 500-sheet ream of 20-pound bond paper weighs 5 pounds, while a 500-sheet ream of 24-pound bond paper weighs 6 pounds.
Bond paper in the United States comes in 17-inch by 22-inch sheets, which is cut into four letter-size sheets. The pound designation of each type of paper comes from the weight of a stack of 500 sheets, so 500 sheets of 20-pound paper weighs 20 pounds. How much fiber is used to make each type of paper determines the actual weight. Paper ranges from 18 pounds for newsprint to 300 pounds for print-making and painting papers.