Every formula, constant and assumption these calculators use, where it comes from, and when it was last checked. If you find something wrong, tell us and we will correct it.
SourcingCalc does not hold a database of rates. It has no duty tables, no carrier price lists, and no exchange rates. Every number used in a calculation is one you type in from your own quotes, your own carrier and your own customs schedule. What the site supplies is the arithmetic and the structure - which costs belong in the comparison, and how they combine. That is a deliberate design decision: rate tables go stale silently and produce confident wrong answers, and a tool that cannot go stale is worth more than a tool that is briefly more convenient.
Because the site stores no rates, there is nothing here that expires. The only durable constants are the dimensional-weight divisors below, which are published industry standards that change rarely, and both of which you can override manually. Everything else is your input.
| Constant | Value used | Basis | Last verified |
|---|---|---|---|
| Express courier dimensional divisor (metric) | 5,000 cm³/kg | Standard published divisor for international express services (FedEx, UPS, DHL). Overridable in the calculator. | 2026-08-11 |
| Express courier dimensional divisor (imperial) | 139 in³/lb | The imperial equivalent of 5,000 cm³/kg, used for US domestic and international express. | 2026-08-11 |
| General air freight divisor (metric) | 6,000 cm³/kg | IATA standard volumetric divisor for air cargo. Individual carriers may apply their own. | 2026-08-11 |
| General air freight divisor (imperial) | 166 in³/lb | The imperial equivalent of the IATA 6,000 divisor (1,000,000 ÷ 6,000 ≈ 166.7 kg per CBM). | 2026-08-11 |
Dimensional weight = (length × width × height) ÷ divisor. Billable weight is the greater of actual weight and dimensional weight, then rounded up according to the carrier's rule. This is why a light, bulky carton costs more than its scale weight suggests.
Total order cost = goods + freight + duty + payment fees + one-time costs. True cost per unit = total order cost ÷ units. The comparator applies this identically to every quote, which is the entire point: quotes are only comparable once the same cost categories are present in each.
Duty is charged on a declared value, and which costs are inside that value differs by country. Many customs regimes - including the EU, UK, Canada and much of the Caribbean - assess duty on a CIF basis (goods plus insurance plus freight), while the United States generally assesses on the FOB value of the goods alone. The comparator lets you pick, because choosing wrong changes the answer materially. Verify the basis for your destination with your customs broker.
Gross profit per unit = sell price − (sell price × channel and payment fee rate) − fulfillment cost − landed cost per unit. Gross margin = gross profit ÷ sell price. The price required for a target margin = (landed cost + fulfillment) ÷ (1 − fee rate − target margin). Note this is gross margin only: it excludes advertising, returns, storage and overheads.
Net revenue per unit sold = sell price × (1 − fee rate) − fulfillment. Break-even units = total cash at risk ÷ net revenue per unit, rounded up. Cash at risk is the whole order cost, which is why a larger minimum order quantity at a lower unit price can still be the worse decision: the per-unit saving is only real on units that actually sell.
If a formula or constant here is wrong, we want to fix it rather than defend it. Email the address in the footer with the page and the correction, and we will either correct it or explain why we disagree, within a few days. Corrections are dated on this page.