Use the balloon payment calculator to estimate the monthly payment and the final lump sum of a given balloon loan construction. Amortization Period.This calculator computes the payment amount necessary for a mortgage with a balloon payment, using monthly interest compounding and monthly payments. A balloon payment is a large one-time amount due at the end of a loan. Mortgages, auto loans, and business loans have been structured for balloon payments. Monthly principal and interest payment (PI). The monthly payment is calculated using the number of payments in the selected amortization period. Adjustablerate mortgages (ARM) and balloon mortgages are two loan products that appeal to borrowers in this environment.