As of June 2014, the base rate of a U.S. first-class postage stamp is 49 cents. This rate applies to standard-sized mailings weighing 1 ounce or less. Twenty-one cents is added for each additional ounce.
Stamps.com states that as of Jan. 26, 2014, the retail rate for a first-class stamp increased by 3 cents. Consumers save when using a meter to purchase a first-class stamp. The rate for a 1-ounce letter is 1 cent less, at 48 cents. The metered mail rate includes online postage and postage meters. First-class flat mail weighing 1 ounce costs 98 cents. This is a 6-cent rate increase from the prior year.