How do you calculate the annual interest rate of 12% compounded monthly. I know how to do for annually but not monthly. You are offered the opportunity to put some money away for retirement. You will receive 10 annual payments of $4,500 each beginning in 26 years. If you desire an annual interest rate of 12% compounded monthly. I know the formula setup is: (4500/((1.12)^26..... etc... I'm not sure how the monthly is calculated Can you advise?