About the Extra Repayment Mortgage Calculator
Paying a little extra off your home loan each month can cut years off the term and save a substantial amount of interest. This calculator compares your standard repayment schedule against one where you add a fixed extra amount every month, and shows the new payoff time, interest saved and time saved.
How it works
- The calculator first works out your standard monthly repayment using the loan amortisation formula for your loan amount, rate and term.
- It then simulates the loan month by month with your standard repayment plus the extra amount applied every month, reducing the balance faster.
- It counts how many months it takes for the balance to reach zero under this faster schedule, then compares total interest and total time against the original loan.
Assumptions and behaviour
- Assumes the extra repayment is applied every month without interruption, and the interest rate stays fixed for the life of the loan.
- Interest is calculated monthly on the reducing balance, consistent with how most Australian home loans compound.
- The simulation is capped at the original loan term to avoid runaway calculations if the extra repayment is very small.
Limitations
- Doesn't account for redraw restrictions, offset accounts, fixed-rate break costs, or lenders that don't allow extra repayments without a fee.
- Assumes the rate never changes — real variable rates move over time, which will change the actual outcome.
- This is general information only, not financial advice. Speak with your lender or a licensed financial adviser about your specific loan.
Privacy
The calculation runs entirely in your browser. Nothing is uploaded or stored.
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