An annual percentage rate (APR) is the annual rate charged for borrowing or earned through an investment. APR does not take into account compounding, while annual percentage yield (APY) does. Borrowers often see APR figures when they compare credit cards or mortgage rates. APR rolls in any up-front fees and charges. The advertised rate, or nominal interest rate, is used when calculating the interest expense on your loan. For example, if you were considering a mortgage loan for $200,000 with a 6 percent interest rate, your annual interest expense would amount to $12,000, or a monthly payment of $1,000. The original principal on a new loan or principal remaining on an existing loan. Interest Rate The annual nominal interest rate, or stated rate of the loan. Number of Months The number of payments required to repay the loan. Monthly Payment The amount to be paid toward the loan at each monthly payment due date.