Postcards are one of the most cost-effective marketing tools a business can use. Due to their size and lack of envelope, they stand out from typical mailed items. With an eye-catching image and succinct wording, most people can't resist giving them a look. The U.S. Postal Service specifies what qualifies as a postcard, and it's important to understand and follow the rules.

Size Restrictions

Postcards are subject to specific height and length measurements. To qualify as a standard postcard, it must be between 3 1/2 and 4 1/4 inches high, and between 5 and 6 inches long. Large postcards are 6 inches high and 9 inches long, while jumbo postcards are 6 inches high and 11 inches long. Both large and jumbo sizes cost more money to mail. The Postal Service considers length to be the side of the card that is parallel to the address, and the height is perpendicular to the length.


Clever graphics and wording will help your postcard get noticed, but don't get creative with the postcard's shape. The U.S. Postal Service requires that postcards be rectangular.

Appropriate Thickness

Postcards mailed through the U.S. Postal Service must be between 0.007 and 0.016 inches thick. The minimum is about as thick as an index card. Thinner pieces may get caught and ruined in the Postal Service's equipment and, therefore, are not allowed.

Attaching Enhancements

Sometimes mailers want to add stickers, magnets or other items to postcards to possibly increase their chances of gaining attention. The Postal Service is particular about which types of enhancements are permitted. Check with a recommended mailpiece design analyst near you to determine if your idea can be mailed.

Addressing Properly

While trying to fit a compelling message onto mail the size of a postcard, it's important not to encroach on the address area -- on the same side as the postage, just as it is on an envelope. The Postal Service requires type at least 8 point in size and prefers the address in all caps. Put the name of the addressee on the first line, followed by the street address, any apartment, suite or unit number, the city and state on the next line followed by the ZIP code. Use the standard, approved two-letter abbreviation. A return address is not required on a postcard; but if you're including one, it goes in the upper left corner of the address area. Leave the upper right corner blank to accommodate postage.