Postage Rates First Class Mail Letter (1 oz.) - Retail/Post Office Rate* $0.73 First Class Mail Letter (1 oz.) - Metered Mail/Stamps.com Rate $0.69 First Class Mail Letter - each additional ounce $0.28 Postcard $0.56 First Class Mail Flat (1 oz.) ...
Stamps work with single-piece First-Class Mail — basically, a standard letter. If you’re using a common no. 10 envelope, your mail will be eligible for letter pricing. Letters can weight up to one ounce. Technically, letters must be a rectangle. They can be up to 6-1/8 inches high...