What Is a Balloon Mortgage Calculator?

A balloon mortgage calculator estimates the monthly payment and the large lump-sum "balloon" payment that comes due at the end of a short fixed period on a balloon loan. Unlike a fully-amortizing mortgage, where each payment chips away at both interest and principal until the balance reaches zero, a balloon mortgage keeps payments low for a set number of years and then demands the remaining principal all at once.

This calculator uses the standard mortgage payment formula to find your monthly principal and interest, then applies the remaining-balance formula to reveal exactly how much you will still owe at the balloon date. It also layers in taxes, insurance, and PMI for a true monthly cost, and projects a refinance scenario so you can plan what happens next.

How the Balloon Payment Is Calculated

The monthly principal and interest payment M is computed with the standard amortization formula:

M = P[r(1+r)^n] / [(1+r)^n - 1]

Where P is the loan amount, r is the monthly interest rate (APR / 12 / 100), and n is the total number of months in the full loan term. The balloon balance after p payments (the balloon term in months) is the unpaid principal:

B = P[(1+r)^n - (1+r)^p] / [(1+r)^n - 1]

This is the amount you must pay — or refinance — when the balloon term ends. Because p is much smaller than n, the balance barely shrinks, which is why the balloon amount is so large.

Planning for the Balloon and Refinancing

The biggest risk with a balloon mortgage is the due date itself. You should decide early whether you will sell, refinance, or pay the balance from savings. Our Advanced Options estimate a refinance at your expected future rate and term, showing the new monthly payment and total interest so you can compare strategies.

If your down payment is below 20%, PMI is automatically added to your monthly payment. Property tax and home insurance are also spread across the year and included in your total monthly obligation. Use the results above to confirm the balloon fits your long-term plan — and remember that rising rates at refinance time can raise your future payment significantly.