How the Balloon Payment Calculator works
A balloon loan keeps monthly payments low by sizing them as if the debt were spread over a long amortization schedule, then demands the whole unpaid balance in one large final payment — the balloon — when a much shorter term ends. This calculator finds that lump sum, the monthly payment behind it, and the interest you pay along the way.
The formula
The calculation runs in two steps. First it computes the fully amortizing monthly payment for the loan amount over the amortization term:
- Monthly payment: M = P × r × (1+r)n / ((1+r)n − 1), where P is the loan amount, r is the monthly rate (APR ÷ 12), and n is the number of months in the amortization term.
- Balloon payment: the balance left after k payments (the balloon term in months) is B = P × (1+r)k − M × ((1+r)k − 1) / r. Because the schedule was built to run for n months but the loan ends at k < n, that balance is still owed as the balloon.
When the interest rate is zero the monthly payment is simply P ÷ n and the balloon is P − M × k. The balloon term must be shorter than the amortization term; if they are equal the loan pays off completely and there is no balloon.
How to read the results
- Balloon payment is the single amount due at the end of the balloon term. Compare it to the original loan amount: a balloon near 90% of the principal means the monthly payments barely touched the balance.
- Monthly payment is what you pay each month until the balloon comes due. Lengthening the amortization term lowers it but raises the balloon.
- Total of monthly payments and total interest paid cover only the balloon term, not a hypothetical full payoff, so you can see the real cost of holding the loan to its balloon date.
Planning for the balloon
Borrowers typically handle the balloon in one of three ways: refinancing the remaining balance into a new loan, selling the financed asset (common with cars and commercial property), or saving toward the lump sum during the term. Run the numbers early so the balloon date is never a surprise, and confirm the exact figure with your lender, since fees and rounding conventions can shift it.