how much to ship a flat rate medium box

how much to ship a flat rate medium box The cost to ship a Flat Rate Medium Box with USPS depends on the shipping service selected. As of 2025, the price for USPS Priority Mail Flat Rate Medium Box is fixed, regardless of the weight (as long as it doesn’t exceed 70 pounds). Domestic rates typically start at around $16.00, and international shipping costs will be higher depending on the destination. This flat-rate option is a cost-effective choice for sending heavy items or products that need to arrive quickly without additional weight-based pricing.