Smallest size envelope you can mail

According to the United States Postal Service (USPS), the smallest size envelope that can be mailed is a #6-3/4 envelope, which measures 3-1/2 inches long, 6-1/2 inches wide, and 1/4 inch thick. This envelope is designed to hold a standard business-sized letter and is the smallest size that can be used for First-Class Mail.

Here are the specific dimensions for a #6-3/4 envelope:

Keep in mind that even though this is the smallest size envelope that can be mailed, it's still subject to certain size and weight restrictions. For example, the envelope must be able to be processed through automated machinery, and it must weigh no more than 3.5 ounces (99 grams).

It's also worth noting that while the USPS has specific guidelines for the smallest size envelope that can be mailed, other countries may have different requirements. If you're planning to mail an envelope internationally, be sure to check with the destination country's postal service for their specific guidelines.