usps flat rate international shipping rates are designed to offer a straightforward pricing structure for shipping packages to international destinations. With USPS Flat Rate International services, customers can ship items to numerous countries at a fixed price, regardless of the weight of the contents (as long as it fits within the size limits of the flat rate box or envelope). For example, the cost to ship a Flat Rate Box to Canada or other destinations typically ranges from around $28 to $65, depending on the destination and package size. These rates are ideal for individuals or businesses who need to send items quickly and predictably, without worrying about fluctuating shipping costs based on weight or distance.