Balloon Mortgage Calculator
A balloon mortgage is a loan where the monthly payments are worked out over a long amortization period, but the loan itself ends early. When it comes due, the balance still owed, called the balloon payment, must be paid in full or refinanced. This calculator shows you the monthly payment, the balloon due, how much you have paid before that point and how much of that is interest.
Use it to test how a balloon loan would look before you speak to a lender. The results are based only on the figures you enter, so treat them as a guide to the maths rather than a quote for an actual loan.
How to use the balloon mortgage calculator
- Enter the loan amount you plan to borrow in pounds.
- Enter the interest rate (APR) as a percentage.
- Enter the number of years the payments are worked out over (the amortization period).
- Enter the number of years after which the balloon falls due.
- Check the balloon payment due, the monthly payment, the amount paid before the balloon and the interest paid before the balloon.
The formula
- Monthly payment = P × r ÷ (1 − (1 + r) ^ −n), where P is the amount borrowed, r the annual rate ÷ 12 ÷ 100 and n the number of months, over the amortization period
- Balloon = P × (1 + r)^k − payment × ((1 + r)^k − 1) ÷ r, where k is the number of months until the balloon is due
- Interest before the balloon = payment × k − (P − balloon)
Worked example
The figures below are made up to show the maths. They are not current prices, rates or product figures.
| Loan amount | £200,000.00 |
|---|---|
| Interest rate (APR) | 6% |
| Payments worked out over (amortization) | 30 years |
| Balloon due after | 7 years |
- Balloon payment due £179,278.77
- Monthly payment £1,199.10
- Paid before the balloon £100,724.49
- Interest before the balloon £80,003.26
Tips for an accurate answer
- Use the APR figure from your lender, as it is the rate the calculator expects.
- Remember the balloon payment is still owed in full when the loan ends, so plan how you will pay it or refinance it.
- Try a few different balloon dates to see how the balloon size and monthly payment change.
- Check the final figures with your lender or bank before making any decision, as they can confirm fees and exact terms.
Questions people ask
How do I calculate my loan to value (LTV) in the UK?
This calculator does not work out loan to value, so it cannot answer that directly. It only shows the balloon payment, monthly payment and interest paid before the balloon, based on the figures you enter. Ask your lender how LTV is measured for your case.
How do I use a balloon calculator?
Enter the loan amount, the interest rate (APR), the number of years the payments are worked out over and the year the balloon is due. The calculator then shows the balloon payment due, the monthly payment, the amount paid before the balloon and the interest paid before the balloon.
What happens at the end of a balloon loan?
At the end of a balloon loan, the remaining balance called the balloon payment is due in one lump sum. You need to pay it, refinance it or otherwise arrange to clear it. This calculator shows how large that balance will be.
What is a balloon mortgage?
A balloon mortgage has monthly payments worked out over a long period, but the loan ends earlier. The remaining balance, the balloon payment, is due in one lump sum at that point. This calculator shows how large that balance will be.
What does the amortization period mean here?
The amortization period is the number of years the monthly payment is calculated over, which is longer than the loan term. Entering a longer amortization period lowers the monthly payment but leaves a larger balloon.
Why is the balloon payment bigger than I expected?
Because the monthly payments are spread over a long amortization period, most of each early payment goes towards interest rather than the original amount borrowed. This means a large balance remains when the balloon falls due.
Does the calculator include fees?
The calculator works only from the loan amount, interest rate and terms you enter, so it does not add lender fees or other charges. Ask your lender for these before deciding.
Should I rely on this result alone?
No. This is a maths tool, not financial advice. Check the figures with your lender or bank before committing to a balloon loan.
Sources
This calculator uses the standard loan and interest formulas above and the numbers you type. It needs no outside figures.
An estimate from the numbers you enter, worked out with the formula shown. It is maths, not financial advice: your lender or bank has the final figures. Page checked 23 Oct 2026. Read the disclaimer