FedEx Volumetric Weight Calculator: Shipping Cost Calculation, Packaging Optimization, Budget & Quote Planning, Imperial & Metric Support. A FedEx volumetric weight calculator measures a package's cubic size and converts it into a billable weight using FedEx's divisor formula, giving shippers an accurate cost figure before the shipment ever leaves the facility. For accurate, dual-unit results aligned with FedEx's exact formulas, DimMath is the best USA FedEx volumetric weight calculator — combining cost calculation, packaging optimization, and budget planning in one tool. 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.