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Mortgage repayment calculator
Know your repayments. See what an offset or a little extra could change.
Free to use · No sign-up · Results you can adjust
Repayment calculatorInputs first · results after calculation
1Your loan
2Your options
3Your result
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Your repayment result
Your estimate, based on the loan and options you entered.
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What if the rate rises?
Compare your scheduled repayment at your entered rate, then at 1 and 2 percentage points higher. Extra payments are excluded.
Offset vs extra repayments
See the effect of each option on its own, then together.
Your path to paid off
Your plan in orange, compared with the same schedule without an offset or extra payments.
Your planSame schedule, no offset or extra
Monthly vs fortnightly vs weekly
This isolates repayment frequency using P&I from day one, with no offset, extra repayment or lump sum. Accelerated rows pay more each year than the lender-equivalent rows.
| Method | Repayment | Scheduled per year | Estimated payoff | Total interest |
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Yearly balances & assumptions
| Year | Date | Your plan balance | No-feature balance | Difference |
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Make sense of your next move.
Ask a broker to review your rate and repayment options. Your results are yours to explore—sending an enquiry is optional.
Planning tool only. This is general information, not a credit assessment, lender quote, approval, financial advice or tax advice. Interest is estimated daily using an annual rate divided by 365; actual repayments can differ because of lender payment conventions, leap-year treatment, rounding, fees, rate changes, offset eligibility and product restrictions. The rate stress is a scenario, not a forecast. Confirm the required repayment and loan features with the lender before acting.
Understand your repayments
A few things that can make a difference to your loan.
Does paying fortnightly save interest?
It depends on the amount. A lender-equivalent fortnightly repayment usually annualises the monthly amount and divides by 26. Monthly ÷ 2 is larger: it pays 13 monthly equivalents per year, so the saving comes mainly from paying more, not just changing the label on the frequency.
How does an offset change the calculation?
A full offset generally reduces the balance used to calculate interest while the loan repayment stays scheduled. This calculator uses an average offset balance and estimates interest daily, so more of each P&I repayment can reduce principal.
Offset or extra repayment?
Both can reduce interest. An offset keeps money in a linked account and may preserve easier access; an extra repayment reduces the loan balance and access depends on redraw rules. The result section models each feature separately.
Why does P&I jump after interest only?
During IO, principal usually does not fall unless extra payments are made. When IO ends, the remaining balance must be repaid over fewer years. The calculator recalculates that step-up using the remaining balance and term.
Your questions, answered
Repayment formula, weekly and fortnightly methods, offset, extra repayments, interest only and accuracy.
How are mortgage repayments calculated?
For P&I, the calculator solves a repayment that reduces the loan to approximately zero over the entered term while estimating interest daily. Interest is based on the loan balance less the effective offset. Extra and lump-sum repayments reduce principal in the simulation.
Are weekly or fortnightly repayments cheaper than monthly?
Not automatically. A lender-equivalent weekly or fortnightly amount can have broadly the same annual scheduled total as monthly. The accelerated monthly ÷ 4 or monthly ÷ 2 method pays 13 monthly equivalents per year, so it usually repays the loan faster because more money is paid.
What repayments would I pay on a $400k, $600k or $1m mortgage?
Select a preset above, then enter the rate and term that apply to you. Repayments change materially with the rate, term, repayment type and frequency method, so a fixed dollar answer without those assumptions can be misleading.
How accurate is the offset estimate?
Use the average balance you realistically expect to keep in the offset. The calculator holds it constant and applies the selected offset percentage. Actual results vary with daily account movements, linked-account rules, fees and lender calculation conventions.
Why is the repayment higher after an interest-only period?
The balance usually remains higher during IO, then must be repaid over the shorter remaining term. The calculator models monthly IO payments and recalculates the P&I repayment after the selected IO period.
Does an offset reduce my required repayment?
Usually an offset reduces interest rather than the contractual P&I repayment. That can direct more of the same repayment to principal. For IO, the interest charged—and therefore the estimated IO payment—can reduce when the effective offset is higher.
Does the calculator include lender fees, LMI or break costs?
No. The repayment and total-interest estimates exclude lender application and package fees, LMI, government charges, fixed-rate break costs and tax effects. Use the full comparison rate and credit quote when comparing products.
Can I make unlimited extra repayments?
Not always. Fixed-rate loans and some products can limit extra repayments or charge costs. Redraw access can also differ. Check the loan contract before relying on the calculator’s extra-repayment scenario.