In the case of Balloon. A balloon payment is an extralarge payment on a loan.It's usually at least twice as big as your average monthly payment, and it can be even larger. This tool figures a loan's monthly and balloon payments, based on the amount borrowed, the loan term and the annual interest rate. This calculator computes the payment amount necessary for a mortgage with a balloon payment, using monthly interest compounding and monthly payments. • Located in the San Antonio city limits.