A swap or rollover rate is determined by the difference in interest rates between the countries involved in a currency pair. For example, if you are trading the Australian dollar against the United States dollar (AUD/USD), the rollover rate calculation would involve the interest rates between Australia and the United States. Whether the position is long or short, a swap rate is applied. Because of this, each currency pair has its own swap rate.
Swap rates can be calculated using the following formula:
Rollover rate = (Base currency interest rate – Quote currency interest rate) / (365 x Exchange Rate).