One first-class stamp is needed to mail a letter that weighs 1 ounce or less to Georgia from anywhere within the United States, as of 2014. There is an added cost for each additional ounce and a limit of 3.5 ounces for letters.
The United States Postal Service requires that letters be at least 3 1/2 inches by 5 inches. Any letter smaller than these measurements cannot be mailed. The maximum size of a letter is 6 1/8 inches by 11 1/2 inches. A larger letter can still be mailed but is classified as a large envelope, which has a higher postage rate.