The number of stamps required for out-of-state mailing varies based on the size and weight of the envelope. A one-ounce envelope of normal size and weight requires a 49-cent stamp.
If a letter weighs more than 1 ounce, an additional 21-cent stamp is required for each additional ounce. A standard-sized envelope weighing 3 ounces, for instance, would require one 49-cent stamp and two 21-cent stamps. It costs the same amount of postage to send a letter to another state as it does to send a letter within the same state.