The size of a postcard can vary, but to qualify for mailing at the First-Class Mail postcard price, it must be rectangular and meet the following dimensions:

• At least 3.5 inches high x 5 inches long x 0.007 inch thick
• No more than 4.25 inches high x 6 inches long x 0.016 inches thick

The most common standard postcard size is 4” x 6” . However, postcards can also be as small as 3.5" x 5" or as big as 6.125" x 11.5" and everything in between. If a postcard fits within those dimensions and is less than 0.25” thick, it can be processed as a postcard by the U.S. Postal Office. Larger postcard dimensions are also available, but they may cost more. Here are some examples of other postcard sizes:

• Small Postcards: 4.13" x 5.83"
• Rack Cards: 3.67" x 8.5"
• Medium Postcards: 5" x 7"
• Large Postcards: 6" x 9" or 6" x 11"
• Jumbo Postcards: 8.5" x 11"

Its important to note that if a postcard does not meet the dimensions above, then it is considered a letter and letter-size postage is charged.