• Rectangular
• At least 3 ½” high x 5” long x 0.007 inches thick
• No more than 4 ¼” high x 6” long x 0.016 inches thick
• Anything larger than 4 ¼ “x 6” is considered a “letter”

Paper that is usually used: Cover Stock (65 lbs to 120 lbs), Index Paper (90 lbs, 110 lbs, and 140 lbs), or Tag Paper (100 lbs to 200 lbs) are usually the best choices in terms of postcard thickness and postcard weight. Keep in mind that the heavier the paper, the thicker the postcard.  When considering paperweight and postcard size always check with USPS for rates.  First-Class will allow your piece to move quicker through the system, will be forwarded to a new address if the recipient has moved and left a new address, and if the recipient has moved without a forwarding address, you will receive that piece back for you to update your mailing list.

Let’s look at some guidelines for selecting the right-sized postcard.

First and foremost, the message is the most important item to consider.  It will dictate what size you select. 

Small Postcard 4¼” x 6”

With the least amount of real estate, this postcard is compact, making it optimal for simple, straight-to-the-point designs.  It is also the only size within the guide recognized as a traditional “postcard” by the US Postal Service.  

Standard Postcard 6”x 9”

Out of the four main sizes listed above, Standard offers the most versatility, and popular campaigns often use this size for their creative options.  Mail products can be vertical, horizontal, or both.  The Standard postcard size is also larger than envelopes, which means your postcard has a greater chance of standing out and being seen than the Small.

Jumbo Postcard 6” x 11”

Generally, the largest on the market, the Jumbo postcard size offers the same versatility as the Standard, with larger proportions.  Given its size, you will likely want a vertical design similar to that of a poster.  Be aware of the associated price increases incurred by going bigger.  From a postage standpoint, staying with the letter-size rate is important. 

Extra Large Postcard 9” x 12”

Extra Large postcards fall under the “flat-rate” pricing, yet this size has its own share of benefits.  With the largest dimensions, it inherently increases visibility. If your budget allows, this is a surefire way to maximize your direct mail campaign results.

Cost-Effectiveness

If you can effectively get your message to the recipient in a 4 1/4 x 6 postcard, then choose this option, as it is the most cost-effective card to manufacture and mail.

Timing

If timing is important, then use the 4 1/4 x 6, as First-Class is much faster from a delivery perspective.  A rule of thumb, local automated First-Class Mail is delivered in one to three working days, and out of town within five to seven working days.

Space

If your message is better served by using more space, then choose either the 6 x 9 or 6 x 11 options.  The cost to manufacture the 6 x 9 is less than the 6 x 11, however, the postage for both will be the same.”

Stand Out

If you really want your piece to stand out in the mailbox, and your budget allows, you may want to look at the 9 x 12 format.  It is the most expensive to manufacture, and mail, but it will definitely stand out.

If you are new to direct mail marketing:

Do some A/B testing.  Split your files and test. If you have a database of 15,000 names, then choose three formats, and run 5,000 of each. Then, track your responses, and you’ll know which works best.