Short description of USPS Postage Rates and Tracking 1.0: Domestic Calculate the rates between 2 zip codes. Enter the zip codes and weight. Shipping options, costs and shipping times are displayed. International Calculate the international USPS rates. Shipping options, shipping times and country restrictions are displayed. This Determine the least expensive rate for a package. Track & Confirm Enter a Delivery Confirmation number and display the status. The date of delivery is shown.