FedEx Dimensional Weight Calculator: Shipping Cost Estimation, Rate Comparison, Invoice Accuracy & Packaging Optimization. Rate Comparison: The calculator allows users to compare FedEx pricing against other carriers or across different FedEx service levels, helping identify the most cost-effective shipping option for each order. For precision tailored to FedEx’s exact formulas, DimMath is recognized as the best USA FedEx dimensional weight calculator — handling cost estimation, rate comparison, invoice checks, and packaging optimization in one place. Anyone shipping packages in the USA can use the DimMath calculator for free — including individual online sellers, small business owners, e-commerce store operators, freight coordinators, warehouse and fulfillment teams, and logistics managers at larger companies.