How big can a postcard be to mail

According to the United States Postal Service (USPS), a postcard can be up to 6 inches (15.24 cm) in length, 4.5 inches (11.43 cm) in width, and 0.007 inch (0.0178 cm) in thickness. This is the maximum size allowed for a postcard to be mailed at the standard postcard rate.

However, it's worth noting that the USPS also has specific guidelines for postcard dimensions, which are as follows:

• Length: 3.5 to 6 inches (8.89 to 15.24 cm)
• Width: 5 to 4.5 inches (12.7 to 11.43 cm)
• Thickness: 0.007 inch (0.0178 cm) or less

If your postcard exceeds these dimensions, it will be considered a letter and will require a larger postage rate.

It's also important to note that some countries have their own specific guidelines for postcard sizes, so if you're mailing a postcard internationally, be sure to check with the destination country's postal service for their specific requirements.

In general, it's a good idea to keep your postcard design within the standard dimensions to ensure it can be mailed at the lowest rate.