Here at Revolut the exchange rates are determined based on the foreign exchange market data feeds that we get from a range of different independent sources, and we don't apply any extra markups.
When exchanging currencies with Revolut, fees may apply depending on several factors. If you’d like to know more, read this FAQ.
For card payments on currencies that you can't hold with Revolut, you can just use your Revolut card and the exchange will be done automatically at the moment of the transaction.
Please note it's not possible to review the exchange rate before making these payments. You can check estimated rates by following this website. Also keep in mind the rates are always changing, and the rate might be slightly different from the one you see on the page.
If you think the exchange rate isn't correct, it's possible that the merchant charged you in your base currency, and applied their own foreign exchange rates/fees. So, even though you had the correct currency available, you were deducted from the main currency (this is called Dynamic Currency Conversion or DCC).