Credit card interest is the cost of borrowing money from a credit card issuer and is determined by your annual percentage rate (APR). Interest charges are calculated based on your average daily balance, which is the sum of your outstanding balances each day of the billing cycle divided by the number of days in the cycle. The interest is then charged on this average daily balance. Read More: https://cardinsider.wixsite.com/cardinsider/post/how-credit-card-interest-works