Extra Repayment Calculator
See how extra mortgage repayments cut years off your home loan — and exactly how much interest you avoid.
Enter your loan amount, rate and term, add an extra repayment, and the calculator models the full mortgage repayment schedule — showing your new payoff date, the interest you avoid, and the principal and interest split for every period.
Open the calculatorInterest avoided
Every extra dollar removes principal that would have accrued interest for the rest of the term.
Years off the term
See the exact payoff date shift, not a rule of thumb.
Full schedule
Period-by-period amortisation showing principal and interest.
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What extra repayments do to a $600,000 mortgage
The table below is generated with the same amortisation engine the calculator uses. It assumes a $600,000 loan over 30 years at 6.5%, repaid monthly, with a scheduled repayment of $3,792.
| Extra / month | Loan term | Total interest | Interest saved | Time saved |
|---|---|---|---|---|
| $0 | 30y 0m | $765,267 | — | — |
| $100 | 27y 10m | $698,103 | $67,163 | 2y 2m |
| $200 | 26y 0m | $643,277 | $121,990 | 4y 0m |
| $500 | 21y 10m | $524,593 | $240,674 | 8y 2m |
Notice that the returns do not scale evenly: $500 a month is five times $100, but saves roughly three and a half times the interest and nearly four times the years. Your own figures will differ — this is illustrative of one loan, not a prediction for yours.
For the reasoning behind why the effect compounds this way, see the guide on how much difference extra repayments really make.
What the calculator gives you
Enter a loan and an extra repayment amount, and the tool produces a complete period-by-period model rather than a single headline number:
- Your revised payoff date and the exact time saved, in years and months.
- Total interest with and without the extra repayment, and the difference between them.
- A full mortgage repayment schedule — every period’s opening balance, interest charged, principal repaid, extra repayment and closing balance.
- Charts showing the balance curve against the same loan without extra repayments, so the gap between the two lines is the interest you avoid.
- Saved scenarios, so you can model $100, $200 and $500 a month and compare them side by side.
It doubles as a mortgage payoff calculator, an amortisation calculator and a principal and interest calculator — all are views of the same underlying schedule.
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Two questions to put to your lender first
Before setting up a regular extra repayment, the modelling is only as good as your lender’s treatment of it. Two things decide whether you actually benefit:
- Does the extra amount shorten my term, or reduce my next repayment? If it lowers the required repayment, the projections above will not hold unless you keep paying the original amount regardless.
- Can I get the money back if I need it? Redraw availability, fees and minimum amounts vary, and redraw is at the lender’s discretion in a way an offset balance is not.
Frequently asked questions
How much faster can extra repayments pay off a mortgage?▾
It depends on your balance, rate and how much extra you pay, but the effect is larger than most people expect because each extra dollar removes principal that would otherwise accrue interest for the remaining term. Modest amounts paid consistently from early in the loan typically shorten the term by several years. Enter your own figures in the calculator to see the exact result for your loan.
Is it better to make extra repayments or use an offset account?▾
Financially the two are close to equivalent, since both reduce the balance interest is charged on. The practical difference is access: money in an offset account stays available, while extra repayments are only accessible through redraw, which your lender controls and can restrict. Many borrowers keep an emergency fund in offset and direct any surplus beyond that to extra repayments.
Will extra repayments reduce my loan term or my repayment amount?▾
This varies by lender and it decides whether you benefit at all. Some lenders keep your repayment the same and shorten the term, which is what pays the loan off faster. Others reduce your required repayment and leave the term unchanged, which cancels most of the benefit unless you keep paying the original amount. Confirm which applies to your loan.
What is a mortgage repayment schedule?▾
A repayment schedule, also called an amortisation schedule, lists every repayment over the life of the loan and splits each one into interest and principal. It shows your opening balance, the interest charged, how much principal you repaid, and the closing balance for each period, so you can see exactly how the debt reduces over time.
Why is so much of my early repayment going to interest?▾
Interest is charged on your outstanding balance, and that balance is at its highest at the start. On a typical 30-year loan the first repayment can be more than 85 per cent interest. As the balance falls the interest charge falls with it, so a progressively larger share of the same repayment goes to principal.
General information only. This page explains how extra repayments generally work. It does not consider your objectives, financial situation or needs, and is not financial product advice under the Corporations Act 2001 (Cth). Figures are illustrative estimates. Speak to a licensed financial adviser before acting.