How our calculations work
Transparent formulas, conservative assumptions and clear limitations.
Input-first calculations
Our calculators use only the figures entered by the visitor. We do not supply hidden carrier rates, tax rates, legal thresholds or marketplace fees. Currency selection changes display formatting; it does not perform exchange-rate conversion.
Return-cost model
The central model adds refund, shipping, handling and other non-recoverable costs, then subtracts realistic recovered inventory value. Recovery should reflect what the business expects to regain through resale, refurbishment or liquidation—not the original retail price.
Partial-refund model
The partial-refund tool begins with the refundable item, tax and shipping components selected by the user, then subtracts entered fees and deductions. It does not determine whether those deductions are lawful or permitted by a marketplace.
Rounding
Calculations use full numeric precision internally and display monetary results to two decimal places. Percentages may be rounded for readability, so manually recomputed totals can differ by a small amount.
Validation and updates
Formulas are tested using hand-calculated examples, boundary values and zero-input scenarios. The methodology is reviewed when a calculation changes. Because the tools do not embed live rates or laws, most pages remain evergreen.
Limitations
Results exclude any cost not entered, including chargeback risk, future customer value, fraud probability, taxes, currency conversion, platform-specific reimbursements and contractual carrier adjustments. Use the result as one input to a documented business decision.
Last reviewed: August 12, 2026.