Example result based on the prefilled values.
Interest Saved
A$38,266.59
New Monthly
A$1,375.77 vs Old: A$1,228.17
Continue your plan
Useful next calculations
When to use this calculator
- Before comparing lenders, brokers, or repayment options.
- When you want to test how a different deposit, rate, or term changes affordability.
- When you need a quick estimate before using a formal quote or agreement in principle.
- When you are stress-testing your budget against a potential rate rise to see the impact on monthly payments.
- When you want to understand the full cost of borrowing — not just the monthly figure — before you commit.
A realistic Australia planning example
Use these sample inputs as a quick scenario test, then change one variable at a time to compare outcomes.
Loan Amount (A$)
A$560,000
Interest Rate (%)
5%
Original Term (Years)
25 years
New Term (Years)
25 years
After entering these figures, review interest saved and new monthly together rather than in isolation — each metric tells a different part of the story. Then rerun the tool with one input adjusted to see which variable has the biggest effect on all three outputs before you settle on a plan.
How to read your results
Interest Saved
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
New Monthly
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
Method & assumptionsAuthoritative sources
This calculator models the effect of making one or more overpayments on a standard capital repayment mortgage. It recalculates the full amortisation schedule from the point of each overpayment, showing how the reduction in principal leads to lower interest charges in every subsequent month. The interest saving figure represents the cumulative difference between the original schedule and the revised one. The calculation assumes the interest rate remains constant throughout the remaining term, which will not be the case if you are on a tracker or variable rate product. It also assumes the lender applies the overpayment immediately to the principal rather than holding it in a suspense account — practices vary, so confirm the arrangement with your lender.
Common mistakes
- !Using an assumption that is not supported by a current local quote, bill, statement or official source.
- !Treating a generic estimate as a lender, provider, payroll or tax authority decision.
- !Mixing monthly and annual inputs without converting them consistently.
- !Forgetting location-specific taxes, fees, eligibility rules or payroll deductions where they apply.
- !Testing only one scenario instead of checking how a cautious assumption changes the result.
What to do next
- Run a second scenario with a cautious assumption so you can see the downside clearly.
- Compare the result with the related calculators below before making a decision.
- Check current local rules, eligibility and provider terms before applying or committing money.
- Keep a record of the assumptions so you can update the estimate when a quote, bill or pay figure changes.
- Use the result to prepare better questions for a lender, provider, adviser or employer rather than treating it as a final answer.
Frequently asked
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