us postal service first class envelope size

us postal service first class envelope size refers to the size limitations for envelopes sent via USPS First-Class Mail. For First-Class Mail, the maximum weight for an envelope is 3.5 ounces. The envelope must be rectangular, and the minimum size is 3-1/2 inches by 5 inches, with a maximum size of 6-1/8 inches by 11-1/2 inches. This size restriction ensures that envelopes can be efficiently processed by USPS, maintaining speed and reliability.