Human: I need to know how to calculate the interest on a loan. Assistant: 
To calculate the interest on a loan, you will first need to determine the annual percentage rate (APR) of the loan, which is usually stated as a yearly rate and is based on the total cost of the loan including fees and interest. Then, multiply the APR by the amount of the loan to find out the interest due for that year. Finally, add the interest due to the principal balance to find the new balance at the end of the year.