Standard Postcard Sizes That Qualify for Mailing

Postcard size is not just a design choice, it directly affects what you pay in postage and how the piece performs in the mailbox. Pick a size that falls outside USPS rules and your “postcard” gets billed as a letter or a flat. Here are the sizes that mail cleanly and when to use each.

The mailable postcard sizes

Size	Mail class	Best for
4 x 6 in	Postcard rate (most economical)	High-volume, budget campaigns
5 x 7 in	First-class/marketing mail	A noticeable step up in presence
6 x 9 in	First-class/marketing mail	Strong standout, still affordable
6 x 11 in	First-class/marketing mail	Maximum impact, EDDM favorite

A true USPS “postcard” rate applies to pieces roughly between 3.5 x 5 and 4.25 x 6 inches. Go bigger and the piece still mails, just at letter or marketing-mail rates rather than the cheapest postcard rate.

Size affects more than postage

A bigger postcard does three things: it gives you more room to sell, it stands out in a stack of mail, and it signals a more serious offer. A 4 x 6 is perfect for a quick reminder or coupon; a 6 x 11 is better for a feature-rich promotion with images and multiple offers.

Don’t forget the layout rules

USPS reserves space on the address side for the address block, barcode, and postage. Keep your design clear of that zone so the piece is deliverable. We design to current USPS templates so your postcard qualifies and presorts for the best rate.

Print postcards that mail right

We print heavyweight, full-color postcards in every standard mailing size and handle the sorting and paperwork. See our postcard and direct mail options, and if you are choosing a strategy, compare EDDM vs. targeted lists. Request a free quote to get started.