postage for first class Postage for First-Class Mail with USPS is an affordable option for sending letters, postcards, and small packages weighing up to 13 ounces. The cost of postage varies depending on the size and weight of the item being mailed. As of the most recent rates, the postage for a single first-class letter starts at $0.66 for a standard letter. For packages, rates are based on the weight and the destination. First-Class Mail is one of the most economical ways to send lightweight items and offers delivery within 1 to 3 business days, depending on the destination.