How to use it
You need two rates. The mid-market rate is the interbank midpoint — the number a search engine gives you for “EUR PLN”, with no margin in it. The rate you were offered is on your statement, or is the payout divided by the amount converted.
Enter any stated fees separately, fixed and percentage. Then, if you want the number that actually changes decisions, put in what you convert in a normal month.
What the results mean
Hidden in the rate is the spread: the amount converted multiplied by the gap between the two rates. Nobody invoices you for it and it appears on no statement as a line.
Stated fee is what you were quoted. Comparing the two is the point of the tool, and the note under the result gives the ratio: on a typical bank transfer the unquoted part is comfortably larger than the quoted one, and where the transfer is advertised as free it is the entire cost.
Effective rate is what the deal came to per unit once everything is counted. This is the only rate worth comparing between providers, because it is the only one that cannot be improved by moving cost from the fee to the spread.
A year at this volume applies the same percentage to twelve months. It is the figure that turns a shrug into a phone call.
A worked example
Ten thousand euros of marketplace payout, converted to złoty. The mid-market rate that morning is 4.30. Your bank gives 4.18 and charges a flat 25 zł.
| Line | Amount |
|---|---|
| Worth at the mid-market rate | 43 000 zł |
| Converted at 4.18 | 41 800 zł |
| Hidden in the rate | 1 200 zł |
| Stated fee | 25 zł |
| Total cost | 1 225 zł |
The quoted price was 25 zł. The actual price was 1 225 zł — forty-eight times more, and 2.85% of the transfer. At the same volume every month that is 14 700 zł a year, which is a salary line, not a bank charge.
Why this is not in the other calculators
Every margin tool on this site works in one currency. That is deliberate: mixing conversion into a margin calculation hides which of the two is the problem.
But the conversion cost is a real cost per unit, and it belongs in your costing. The clean way is to work out the percentage here, then add it as a cost line in the product costing or straight into the FBA calculator alongside the referral fee. Three percent of revenue is roughly what a marketplace takes in category fees on electronics; it deserves the same attention.
Where the money usually is
Marketplace payouts. Amazon and others will convert for you and take a spread for it. Receiving in the sale currency and converting yourself is usually cheaper, and it is a setting, not a negotiation.
Card payments from suppliers. When a terminal or a checkout offers to bill you in your own currency, that is dynamic currency conversion, and the spread is set by the party offering it. Paying in the merchant’s currency and letting your own bank convert is almost always cheaper.
Supplier invoices in a third currency. Buying in dollars, selling in euro, banking in złoty means two conversions per cycle. The percentage from this calculator applies to each of them.
Small, frequent transfers. A fixed fee that looks trivial on 10 000 € is punitive on 400 €. Run both through the calculator: the percentage, not the fee, is what to compare.
Why there is no rate table here
Other tools on this site carry a dated dataset. This one deliberately does not, and the reason is not laziness: an exchange rate is specific to a provider, a day, a corridor and often a customer. A table of rates would be stale before it was published, and a stale rate here would produce a confidently wrong answer rather than a missing one.
So both rates are yours to supply. The calculator knows nothing and invents nothing — it subtracts.
Frequently asked questions
Any search engine, or a rate site, for the day of the conversion. It is the midpoint between buy and sell, so no provider actually gives it to you — that is the point of using it as the yardstick.
The transfer may be. The conversion is not. Put the rate you were given into the calculator with a zero fee and the whole cost will show up in the spread — which is exactly what “free” is paying for.
It varies enough by provider and corridor that quoting a benchmark here would be inventing one. Calculate your own effective rate, then calculate an alternative the same way and compare the two percentages. That comparison is reliable in a way an industry average is not.
Different problem. This calculator measures the cost of converting at today’s rate; hedging is about the rate moving between the sale and the payout. Fix the conversion cost first — it is certain, recurring and usually larger than the currency movement on a short cycle.
Not the VAT you charge, which follows the invoice currency and the rules of the destination. It does affect what you actually keep, so it belongs in your margin, not in your tax calculation.