The number of stamps needed for sending a letter out of state varies depending upon the size and weight of the envelope. A standard sized envelope weighing no more than 1 ounce requires one 49-cent stamp.
If a letter weighs more than 1 ounce, it is necessary to add an additional 21-cent stamp for each additional ounce. For example, a standard-sized envelope that weighs 3 ounces would require one 49-cent stamp and two 21-cent stamps. Mailing a letter to another state requires the same amount of postage as it does to mail a letter within the same state.