Postage Rates 2024 Postcard Size. Changes by usps for postcards, flats & letter size explore the usps postage rate shifts for postcards, flats, and letter sizes in 2024, and optimize your mailing strategies accordingly to. See how new and upcoming postage rate changes will affect your shipping, including stamp costs, flat rates, and more.

Oversized options, find mailing costs, and get tips for successful postcard campaigns. Postal services, like the united states postal service (usps), categorize mail by size and weight.