What is the maximum size of a postcard?

The maximum size for a postcard is established by the USPS to ensure that postcards can be processed efficiently and fit the requirements for mailing. The dimensions of 4 1/4 inches in height and 6 inches in length conform to the definition of a standard postcard. This size allows postcards to be easily handled by postal equipment and ensures they are deliverable without any special handling requirements.

Postcards must not exceed these dimensions in order to qualify for postcard pricing, which is typically lower than standard letter rates. By adhering to this maximum size, mailers can ensure their postcards are cost-effective and will be accepted by the USPS without issue. In contrast, larger dimensions would classify the mailpiece differently, often incurring higher postage costs and different handling procedures.