size of first class mail

size of first class mail is a critical factor when determining how much it will cost to ship a letter or small package through USPS First-Class Mail. First-Class Mail is designed for sending lightweight items such as letters, postcards, and small packages. The maximum size for First-Class Mail letters is 6-1/8 inches high by 11-1/2 inches long, and the maximum weight is 3.5 ounces. For parcels, the maximum weight is 13 ounces, with size limitations for both length and girth. First-Class Mail is the most affordable USPS service for sending lightweight items and offers delivery within 1-3 business days, depending on the destination.