The mortgage payoff calculator helps you find out. Use this free Illinois mortgage calculator to estimate your monthly mortgage payments and annual amortization.With our mortgage payoff calculator, discover how much you could save on your mortgage. Use this calculator to see what it will take to pay off your credit card balance, and what you can change to meet your repayment goals. Our online calculators provide quick and easy access to mortgage calculators and information for the public interest. Take control of your finances. NerdWallet's early mortgage payoff calculator figures out how much more to pay. The unpaid principal balance, interest rate, and monthly payment values can be found in the monthly or quarterly mortgage statement. Unpaid principal balance. There are three fields to fill in: home price, down payment and mortgage interest rate.