Methods and systems for estimating shipping costs with at least one vendor are provided, including methods and systems for determining shipping rates with high accuracy and scalability, for any shipment of certain characteristics and service levels. Methods and systems include a database containing information on contracted shipping rates, zone mappings, and accessorial charges with at least one vendor. When this information used in conjunction with information about a package's shipping origin, shipping destination, dimensions, weight, and eligible service levels to estimate the shipping cost of a package for at least one vendor.