You can look up what MasterCard's conversion rate is: https://www.mastercard.us/en-us/personal/get-support/convert-currency.html https://www.mastercard.us/en-us

You can look up what MasterCard's conversion rate is: https://www.mastercard.us/en-us/personal/get-support/convert-currency.html https://www.mastercard.us/en-us/personal/get-support/convert... For a major currency pair, like EUR-USD or JPY-USD, you can see that it's less than a tenth of a cent off the 'real' rate.