What Is the Formula to Calculate Exchange Rates? The formula for calculating exchange rates is to multiply when exchanging from base currency to a secondary currency, and to divide when vice-versa. Therefore, if the EUR/USD exchange rate is 1.30 euros, and $100 is to be converted into euros, the formula is $100 divided by 1.3, giving 76.92 euros. The Nominal Exchange Rate: The nominal exchange rate (NER) is the relative price of currencies of two countries. For example, if the exchange rate is £ 1 = $ 2, then a British can exchange one pound for two dollars in the world market. Similarly, an American can exchange two dollars to get one pound. Mathematically, the real exchange rate is equal to the nominal exchange rate times the domestic price of the item divided by the foreign price of the item. When working through the units, it becomes clear that this calculation results in units of foreign good per unit of domestic good.