Calculator
Loan Repayment Calculator
Estimate repayments, total interest and the effect of rate or term changes before you speak with a lender.
Start with your loan, then explore a different rate or repayment strategy. Rates shown are hypothetical inputs, not offers.
Please check the highlighted fields. Results are hidden until all active inputs are valid.
Offset, extra repayments and accelerated payments
Recalculated repayments use 12, 26 or 52 payments per year. Accelerated fortnightly payments are half the monthly payment; accelerated weekly payments are a quarter. Both pay the equivalent of 13 monthly payments per year during principal and interest. Monthly is unchanged. Interest-only payments cover actual interest and do not accelerate principal by themselves.
The offset is a constant average balance kept separate from the loan. It reduces interest, not the contractual principal and interest repayment. Extra repayments use separate funds: do not also include them in your offset balance. We convert extras to an equal annual amount paid with each regular repayment, so actual payment dates may give different results.
Compare current and proposed loans
Compare the same amount, repayment frequency and interest-only duration, with recalculated repayments and no offset or extras on either loan. Switching costs are paid upfront, not added to the loan. Strategies above apply only to your current loan.
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Break-even uses cumulative interest avoided after upfront costs, adjusted for different principal repayment timing. It is shown only if the saving persists through both modelled schedules. It is not based on a lower repayment alone, and excludes ongoing fees and the time value of money.
How your balance changes
Outstanding loan principal, including any amount still owing at the end. Offset funds are not subtracted from this balance.
Current baselineCurrent with strategyProposed baseline
View balances as a table
| Years | Current baseline | With strategy | Proposed |
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Test a higher interest rate
Hypothetical constant-rate scenarios, not forecasts or lender assessments. These show required repayments on the current amount and term, excluding offset, extras and acceleration. Interest-only loans also show the repayment on reversion.
| Annual rate | Initial repayment | After interest only |
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Optional. Your summary stays in this browser tab until you choose to send an enquiry.
Calculation assumptions
We charge interest each repayment period at the annual rate divided by 12, 26 or 52, on the opening loan balance less a constant average offset, with a floor of zero. Payments occur at the end of the period. Interest-only payments cover that period's interest; any extra reduces principal. On reversion, the repayment is recalculated on the actual remaining principal over the remaining term, without reducing it for offset funds. If interest only lasts the whole term, principal remains due at maturity.
Rates and offset balances stay constant. Totals use full precision and the final payment is limited to the amount owing. No daily interest, fees, tax, redraw, offset withdrawals or rate changes are included, except entered upfront switching costs in the comparison. Estimates only; lender calculations and available loan features may differ. Results do not indicate loan approval. You can use this calculator without entering contact details.
Want these numbers checked? Send the result across and we'll tell you what a lender would make of it. No meeting required.
Use this as a guide, then check the structure
A repayment calculator is useful for seeing whether a loan amount is comfortable, but it does not tell you whether a lender will approve the deal or whether the structure is right. Offset accounts, split loans, interest-only periods, repayment buffers and future borrowing plans can change the best answer.
For a commercial facility with an interest only period, balloon and establishment fee, use our business loan calculator to see the staged repayments and total cost.
For a proper check, send the result through or book a short finance call.
Frequently asked questions
How are home loan repayments calculated?
A principal and interest repayment comes from a standard amortisation formula using three inputs: the loan amount, the interest rate and the term. Early repayments are mostly interest, and the principal share grows as the balance falls. Interest only repayments are simply the balance multiplied by the periodic rate, so the balance never reduces. This calculator runs both, and shows total interest alongside the repayment so you can see the real cost of the term you pick.
Does paying fortnightly instead of monthly save interest?
It depends on how the fortnightly figure is set. Splitting a monthly repayment exactly in half and paying it 26 times a year means you pay the equivalent of 13 monthly repayments instead of 12, and that extra amount cuts the balance and the total interest. If the fortnightly figure is instead calculated to be exactly equivalent to the monthly one, the saving disappears. Check which one your lender is actually doing before assuming a benefit.
What does interest only cost over the life of a loan?
More, because nothing comes off the balance during the interest only period. The repayment is lower while it runs, then rises when the loan reverts to principal and interest over a shorter remaining term. Interest only has real uses, particularly on investment debt or where cash flow is temporarily tight, but it is a cash flow decision rather than a saving. Switch the repayment type in this calculator to see the total interest difference on your own numbers.
How much difference do extra repayments make?
More than most people expect, because every extra dollar reduces the balance that interest is charged on for the whole remaining term. The earlier in the loan you make them, the larger the effect. Enter an extra repayment in this calculator and it models the reduced balance and shorter term. Before committing to extra repayments, it is worth checking whether an offset account gives you the same interest saving while keeping the money accessible.