The number of sheets of paper that can be sent using a single First-Class postage stamp depends on how thick the paper is. For normal-weight writing paper, such as 20-pound paper, about six sheets can be mailed.
Up to 1 ounce can be mailed by First-Class Mail in a regular-size envelope for the price of a stamp, which is 49 cents as of May 2014. Thick paper, such as art paper, is heavier and reduces the number of sheets contained in an ounce, thus lowering the number of sheets that can be sent with one stamp. If the mailing exceeds 1 ounce by even a fraction, then additional postage is required in the amount of 21 cents per additional ounce, up to the maximum letter weight of 3.5 ounces.