1st Class Mail Prices from USPS are one of the most affordable options for sending letters and small packages within the United States. USPS First Class Mail is commonly used for sending lightweight items, such as documents, small packages, and postcards. The pricing for First Class Mail varies depending on the size, weight, and destination of the package. For example, sending a letter within the U.S. starts at just $0.66, while prices increase for larger or heavier packages. This service is ideal for businesses looking for an affordable shipping method with a relatively fast delivery time, typically ranging from 1 to 3 business days.