Approximately six sheets of 20-pound paper weigh 1 ounce together. Each sheet of paper weighs approximately 16/100 of an ounce, so six sheets weigh 96/100 of an ounce.
Because a standard postage stamp covers the mailing of 1 ounce, it is important to include the weight of the envelope when calculating postage. One standard envelope is approximately equivalent to one sheet of paper, as can be seen if the envelope is torn apart at the glued seams and spread open. It is possible to mail five pages of 20-pound paper within a standard white envelope for the cost of one stamp. If one is using heavier or lighter paper, the number of sheets that add together to form 1 ounce changes.