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What Should I Know About Postcard Size?

When it comes to postcard sizes, the most common format is the standard size, which in the United States is typically 4 inches by 6 inches. This size qualifies for the USPS First-Class Mail postcard rate, making it a cost-effective option for mailing. However, postcards can range in size up to 6.125 inches by 11.5 inches, which still qualifies for standard letter rates. It's important to note that the size of your postcard can affect the postage cost, with larger sizes potentially incurring higher fees. According to the United States Postal Service, to qualify for the postcard rate, items must be at least 3.5 inches high by 5 inches long and no more than 4.25 inches high by 6 inches long.

For those looking to stand out, oversized postcards can offer more space for creative designs and content, but keep in mind that they will cost more to send. When designing a postcard, also consider the aspect ratio (length divided by height), which should be between 1.3 and 2.5 to meet USPS requirements. This ensures that your postcard won't incur any additional fees for being nonmachinable. Remember, the material and thickness of your postcard also play a role; it should be sturdy enough to withstand the mailing process without getting damaged. For international mailing, sizes and rates can differ, so it's wise to check with the local postal service for specific guidelines.

Jessica Pestka
Jessica Pestka

Postcards are an inexpensive way to send a quick greeting or a marketing message. Not only is the postage cheaper for a postcard, but the absence of an envelope makes the materials cheaper as well. This lower cost coupled with the fact that a consumer is more likely to read a postcard's message prior to throwing it out, makes them a wise choice for direct marketing. In order to qualify as a postcard and get the lower rate, however, it must be within certain size limits and of a specific shape.

In the US, first class postage for a postcard is about 40% less than first class postage for a letter. Postcards for personal use are typically sent using this standard first class postcard rate. A bulk or automated rate is available for sending a large volume, and it reduces the cost of sending the card even further.

Postcards can be used to send quick messages.
Postcards can be used to send quick messages.

In order for a piece of mail to qualify as a postcard, it must meet several requirements set by the United States Postal Service. Postcard size is an important requirement for any piece of mail being sent with a first class postcard stamp. If the size requirements are not met for a postcard, the item may not be delivered, as postcards do not always include a return address.

The U.S. Postal Service has the following requirements for postcards sent using a postcard rate:

  • Postcards must be at least 3.5 inches (8.89 cm) high, 5 inches (12.7 cm) wide and 0.007 inches (0.018 cm) thick.
  • They can be no larger than 4.25 inches (10.8 cm) high, 6 inches (15.2 cm) wide and 0.016 inches (0.041 cm) thick.
  • The postcard must be rectangular in shape.
  • It cannot contain any stickers or attachments that make it larger or thicker than the above size.

A postcard size or shape outside of the above dimensions can be sent via the U.S. Postal Service, it simply requires a more expensive letter stamp for mailing. When in doubt, the mailer can use a letter stamp or ask the local Post Office the amount of postage needed. A good rule of thumb to follow is that a postcard must be 0.5 inch (1.27 cm) taller and at least as wide and as thick as an index card.

Postcards sent with an automation or bulk rate have even more stringent requirements for size and shape. These requirements are available from a local post office, who can help you determine if the postcard meets the specifications for automation rates. Pre-stamped postcards that conform to the postal requirements are also available for purchase directly from the post office.

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Discussion Comments


@betterment - You should probably at least glance at those postcard mailing size advertisements. Most of the businesses that send those out include a coupon on them. So if it's a service you've been looking for, the coupon could help you save some money.


Well, this explains why I get so many advertisements in the mail that are the shape and size of a postcard. If I had a business, I would definitely want to take advantage of a cheaper option to send advertisements, and it sounds like postcard advertisements are it.

That being said, the businesses that send me those postcards don't have any luck, because I just throw them in the recycling. I find advertisements through the mail to be pretty annoying.


@indemnifyme - I've never really thought about that use for postcards either. I mostly just send postcards if I go out of town, because they really are cheap to buy. I remember buying a bunch of postcards when I took my last vacation and spending under a dollar a piece. It's a shame consumers can't pay cheaper postage for postcards like businesses can.


@John57 - Sending out invitations on a postcard is actually a really good idea, especially if you're sending invitations to a lot of people. It sounds kind of cheap at first, but postage can really add up.

I personally think email is great for stuff like that, but some people find sending an email invite only to be kind of tacky. So using postcards that are the standard postcard size sounds like it would be a nice compromise between sending invitations in envelopes and sending an email invite to something.


I handled much of the marketing at a small company, and we often used prepaid post cards for many direct mailing campaigns. Usually the ones you buy from the post office are pretty plain looking, so if you want to use something that will really catch someone's eye, you may want to go a different route.

We seemed to have the best results when we sent a typical postcard size, but used a bright color or eye catching photograph on the front. The person who receives this, will usually at least glance at it before immediately assuming it is junk mail.


Sending postcards can save you some money, especially if you are mailing a large number of pieces of mail. If you are sending invitations to a wedding or an important life event, you want probably want to use something much nicer than a postcard.

But if you are sending out invitations for a casual party, or appointment reminders, mailing a post card can save you time and money. You don't have to worry about licking all those envelopes and it won't cost you as much to mail as it would a letter.

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    • Postcards can be used to send quick messages.
      By: A_teen
      Postcards can be used to send quick messages.