This calculator helps determine your loan or line payment. For a loan payment, select fixed-term loan.Balloon Payment Loan Calculator. Enter the first three or four fields, then press the button to solve. Use this calculator to look at a variety of possible loans. Change your monthly payment, loan amount, interest rate or term. The calculator will then generate an attractive, detailed report outlining the payments owed and the due dates. Use the balloon payment calculator to estimate the monthly payment and the final lump sum of a given balloon loan construction. This tool figures a loan's monthly and balloon payments, based on the amount borrowed, the loan term and the annual interest rate. Monthly principal and interest payment (PI).