usps how much is priority mail? USPS Priority Mail rates are based on the weight and size of the package as well as the destination. For example, as of 2023, a small flat-rate box costs around $9.95, while the rate for larger boxes and packages may increase depending on the weight and delivery zone. Priority Mail is one of the most popular shipping options for both individuals and businesses due to its speed (1-3 business days) and included features like tracking and $100 of insurance. For more accurate pricing, customers can use the USPS online price calculator.