How much postage to Mail an envelope weighing 2.5 ounces?

The postage required to mail an envelope weighing 2.5 ounces depends on the destination and the service you choose. In the U.S., as of 2023, a First-Class Mail stamp covers up to 1 ounce, with additional ounces costing extra. For a 2.5-ounce envelope, you would typically need one First-Class stamp and an additional charge for the extra 1.5 ounces. It's best to check with the USPS website or visit a local post office for the most accurate rates.