$1.45 Stamps for Wedding Invitations

In 2020 if you are mailing your "large envelope" wedding invitations and it weighs 4 oz you will need a $1.45 stamp to mail it 1st-class. Letters are considered "large envelopes" or "flats" if they measure greater than 6-1/8 inches high OR 11-1/2 inches long OR 1/4 inch thick. You can determine if your letter is a standard letter or a large envelope by using our postage calculator, but be sure to double-check the weight of your invitations with your local USPS post office.