How to use the Yahoo Finance credit card payoff calculator The Yahoo Finance credit card debt calculator gives you a clear picture of how many months it will take to pay off your debt. Simply input your balance, interest rate, and monthly payment amount, and we’ll do the rest. Alternatively, you can set a goal for how many months you want to pay off your debt, and we’ll tell you how much your monthly payment will have to be to achieve that goal. Pay off debt with a balance transfer credit card Credit ...