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Demystifying USPS Requirements: A Comprehensive Guide to Postcard Size and Thickness


In today’s digital age, where emails and text messages dominate communication, there’s still something uniquely charming about receiving a physical postcard in the mail. Whether it’s a picturesque landscape from a far-off destination or a heartfelt message from a loved one, postcards hold a special place in our hearts. However, before you rush to send out your next batch of postcards, it’s crucial to understand the USPS requirements regarding their size and thickness to ensure they reach their destination without any hiccups.

The Importance of USPS Guidelines

The United States Postal Service (USPS) has specific guidelines in place to ensure the smooth processing and delivery of mail, including postcards. Adhering to these guidelines not only helps prevent delays but also ensures that your postcards qualify for standard postage rates, saving you time and money in the long run.

Postcard Size: What You Need to Know

When it comes to postcard size, the USPS has established clear parameters to ensure uniformity and efficiency in mail processing. According to USPS guidelines, a postcard must meet the following size requirements:

  • Minimum Size: A postcard must be at least 3.5 inches high by 5 inches long.
  • Maximum Size: A postcard must not exceed 4.25 inches high by 6 inches long.

It’s essential to note that postcards falling outside these size specifications may incur additional postage fees or even risk being classified as letters rather than postcards.

Understanding Postcard Thickness Guidelines

In addition to size, the USPS also regulates the thickness, or “paper stock,” of postcards. This ensures that postcards are flexible enough to withstand the rigors of automated mail processing equipment without causing jams or damage. Here’s what you need to know about postcard thickness:

  • Minimum Thickness: Postcards must have a minimum thickness of 0.007 inches (approximately 0.18 millimeters). Anything thinner may be subject to damage during processing.
  • Maximum Thickness: Postcards must not exceed a maximum thickness of 0.016 inches (approximately 0.41 millimeters). Exceeding this thickness could result in additional postage fees or rejection by automated processing equipment.

By adhering to these thickness guidelines, you can ensure that your postcards meet USPS standards for efficient processing and delivery.

PO Addresses and Postcard Etiquette

Now that we’ve covered the technical aspects of postcard size and thickness, let’s address another crucial element: the recipient’s address, particularly when it comes to what is PO boxes.

A PO (Post Office) box address is a secure and convenient way for individuals and businesses to receive mail. When addressing a postcard to someone with a PO box, it’s essential to include the recipient’s full name, followed by the PO box number and the city, state, and ZIP code. For example:

John Smith

PO Box 1234

Anytown, USA 12345

Including the recipient’s full name ensures that the postcard reaches the intended recipient, even if they share the PO box with others.

Tips for Designing Postcards

Beyond meeting USPS requirements, designing an eye-catching postcard can enhance its appeal and make it stand out in the recipient’s mailbox. Here are a few tips to consider when designing your postcards:

  • Use High-Quality Images: Whether it’s a scenic landscape or a product showcase, use high-resolution images that capture attention and convey your message effectively.
  • Keep It Concise: With limited space available, keep your message short, sweet, and to the point. Use compelling headlines and concise copy to grab the recipient’s attention.
  • Add a Personal Touch: Consider adding a handwritten note or signature to personalize the postcard and make the recipient feel valued.


Sending postcards is a timeless tradition that allows us to connect with loved ones, customers, or clients in a personal and meaningful way. By understanding the USPS requirements for postcard size and thickness, as well as proper addressing etiquette, you can ensure that your postcards reach their destination smoothly and efficiently.

Whether you’re promoting your business, sharing vacation memories, or simply saying hello, adhering to USPS guidelines and incorporating thoughtful design elements will help make your postcards memorable and impactful.

So go ahead, unleash your creativity, and send a little piece of joy through the mail—it’s a gesture that never goes out of style.

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