Currency rate is calculated as ratio between buying rate for original currency and selling rate for requesting currency. E.g. if buying rate for EUR is 7.30 and selling rate for USD is 5.00 than ratio is 7.30/5.00=1.46. That means that for every 100 EUR you will get 100*1.46 = 146 USD. Currency calculator on our first page will help you with these calculations.