This tool figures a loan's monthly and balloon payments, based on the amount borrowed, the loan term and the annual interest rate. For purchases and refinances, a Middlesex mortgage can help you save money with competitive rates on fixed and adjustable options.Use the balloon payment calculator to estimate the monthly payment and the final lump sum of a given balloon loan construction. Do you need help understanding your debt financing terms? With our Rate Assurance Program, we protect you from rising interest rates for up to 90 days while you search for your new home.