As of October 2015, the cost of a first-class postage stamp in the United States is 49 cents. This rate applies to standard-size mail that weighs one ounce or less. Letters that weigh more than one ounce cost an additional 22 cents to mail
On May 31, 2015, the U.S. Postal Service implemented new postage rates, for the Metered Mail category, with the cost for First Class Mail Letters going from 48 cents to 48.5 cents. The cost to mail a postcard went up one cent, from 34 cents to 35 cents. The First Class Flat rate, at one ounce, remained 98 cents in 2015, but each additional ounce rose to 22 cents.