Currency exchange cost calculator
What an exchange really costs: spread, percentage fee and flat charge together.
Fill in the fields and the result will appear here automatically.
Compare exchange terms using a manually entered baseline rate, spread and charges. For a sale, the amount is foreign currency; for a purchase, it is a budget in local money. The rate always means local money per one foreign currency unit. Set the spread to 0% when entering a final quoted rate, so its markup is not counted twice.
How it works
Formula and logic
Let A be the amount, r the baseline rate, s the spread fraction, c the commission fraction, and F the fixed charge in local money; divide percentages by 100. Selling: Q = A × r × (1 − s) × (1 − c) − F. Buying: Q = (A − F) × (1 − c) / [r × (1 + s)]. Buying first deducts the fixed charge from the budget, then charges commission on the remainder. This is the stated model order, not a rule all banks follow. Loss is A × r (selling) or A / r (buying), minus Q. Monetary rows are normally rounded independently to two decimals; with no spread or charges, the payout equals the baseline exchange.
Example
Teaching inputs: baseline rate 2 local units per foreign unit, spread 10%, commission 5%, fixed charge 20 local units. Selling 1000: 1000 × 2 × 0.9 = 1800; commission 90; payout 1800 − 90 − 20 = $1690, loss 310 / 2000 = 15.5%. Buying with a budget of 2000: (2000 − 20) × 0.95 / 2.2 = 855 currency units, loss 145 / 1000 = 14.5%. This is not a current market rate.
Fields and units
- What you are doing — list option
- Amount to exchange — foreign-currency units when selling; payment-currency units when buying
- Exchange rate — payment-currency units per 1 foreign-currency unit
- Spread on the rate, % — unitless
- Commission, % — unitless
- Flat charge — payment-currency units
How to use
- — Choose selling or buying; the amount label and unit change.
- — Enter the baseline rate in local money per foreign currency unit.
- — Enter the spread relative to that baseline and the percentage commission.
- — Enter the fixed charge in local money in both directions. Compare the payout and the loss relative to the baseline.
Method and limitations
- Calculation method
- Formula and logic
- Limitation
- Teaching model of manually entered terms. The local money symbol does not establish a country, currency pair or contract rules. Check the currency and order of each charge with your provider.
FAQ
Which rate avoids counting the spread twice?
Enter the baseline rate before the spread. If you only know a final quoted rate, use it with a 0% spread; the loss comparison will then use that entered rate as its baseline.
Which currency is the fixed charge in?
Local money, for both selling and buying. For a purchase, the result converts the charge into foreign currency at the spread-adjusted rate so it can be compared with the payout.
Why is the fixed charge handled differently for a purchase?
A sale receives local money and then pays the fixed charge. A purchase pays that charge from the local budget first and commission applies to the remaining budget. A contract using a different order or fee currency needs a different model.
Can the payout be negative?
No. Charges exceeding the available amount produce an error. A zero payout is allowed when charges consume the entire amount; the loss share is then 100%.
What is not included automatically?
Market quotes, taxes, restrictions and transfer charges are not loaded. Only add a transfer charge to F if it uses the same local money and follows the stated model order.