Mortgage calculator for Australian home loans

Monthly repayments by loan size and interest rate

Principal-and-interest repayments over 30 years, computed with the same function as the calculator above so the published figures and the tool always agree. The rate columns bracket where owner-occupier variable pricing sits with the cash rate at 4.35% after three increases during 2026. Planning estimates, not lender quotes.

Read the table across to price a rate move rather than a rate level. On a $700,000 loan, every 0.25 percentage points adds roughly $115 a month — so the three increases during 2026 moved a repayment of this size by several hundred dollars, without the loan balance changing at all. Read it down and each extra $100,000 borrowed costs about $618 a month at 6.29%.

General information only — not personal credit advice or a rate quote. Figures assume a constant nominal rate, no fees, no offset or redraw activity, and no interest-only period. Your lender accrues interest daily and will produce a slightly different number.

Monthly vs fortnightly repayments and total interest

The same loans at 6.29% over 30 years, paid monthly and then fortnightly. Most Australian lenders set a fortnightly repayment at half the monthly figure, which means 26 half-payments a year instead of 24 — the equivalent of one extra monthly repayment, paid without ever deciding to make it.

The pattern is the same at every loan size: switching to fortnightly clears a 30-year loan in about 24 yrs 4 mo and saves $191,765 on $700,000. There is one condition, and it is worth asking your lender directly: the saving only exists if the lender sets the fortnightly figure at half the monthly one. Some instead divide the annual repayment by 26, which spreads the same money differently and saves almost nothing.

General information only — not personal credit advice or a rate quote. Total interest assumes the rate holds for the full term, which no variable loan does.

How a mortgage repayment is actually calculated

A principal-and-interest repayment is the fixed amount that clears the balance to zero over the term, given the rate. Interest is charged on the balance that remains, so the split between interest and principal inside that fixed payment shifts every month. On the $700,000 loan at 6.29%, the first repayment of $4,328 is $3,669 interest and only $659 principal. That ratio is why the balance appears to barely move in the first few years, and why extra repayments made early are worth several times the same dollars paid late.

Your lender will produce a slightly different figure to this calculator, and the difference is not an error in either. Australian lenders accrue interest daily on the closing balance and debit it monthly, so the exact amount depends on how many days fall in each cycle and on the timing of any redraw or offset activity. This calculator uses the monthly convention — annual rate divided by twelve — which is the standard for comparison and is what a lender quotes when it advertises a repayment. Expect agreement to within a few dollars, not to the cent.

One more distinction that costs people money: enter the nominal rate, not the comparison rate. The comparison rate exists to bundle fees into a single advertised number and is calculated on a $150,000 loan over 25 years, which is not a loan anyone writes any more. Interest is charged at the nominal rate. Using the comparison rate here overstates the repayment.

Why a lender will not lend at the repayment you can see here

Affordability is assessed at a higher rate than the one you pay. APRA’s serviceability buffer, reconfirmed in May 2026, requires lenders to satisfy themselves you could still meet repayments 3 percentage points above the product rate. On the $700,000 loan that means testing $5,779 a month at 9.29% rather than $4,328 at 6.29% — a gap of $1,451 a month that you never actually pay but must be able to demonstrate you could. Two other things reduce the number further: lenders substitute an expense benchmark such as the Household Expenditure Measure where declared expenses look implausibly low, and credit card limits count in full whether or not the card is used.

Since 1 February 2026, APRA has also capped high debt-to-income lending: no more than 20% of a lender’s new owner-occupier loans, and separately 20% of its new investor loans, may be written at a DTI of six times income or above. This is a limit on the lender’s book, not a ban on the borrower. A bank can write your loan above six times and remain compliant — it is managing a quota, so the practical effect is a narrower window and closer scrutiny rather than an automatic decline. Construction of a new dwelling, purchase of a newly erected dwelling and bridging finance are exempt. Coverage that describes this as a six-times cap on borrowers is describing something that does not exist.

What moves the repayment after settlement

On a variable loan the repayment is recalculated whenever the rate moves. The cash rate is 4.60% from 30 September 2026, after a unanimous rise on 29 September. Your lender chooses when the repayment changes. Each 0.25 percentage point increase adds roughly $115 a month to a $700,000 loan. Some lenders hold the repayment constant and extend the term instead, which quietly costs more interest — worth checking which your lender does when the notice arrives rather than after the direct debit has already changed.

• Extra repayments. Anything above the scheduled amount comes straight off the balance, so it saves interest at your full rate for every remaining year of the loan. On a 30-year loan the first years are where this compounds hardest, because that is where the interest share of each repayment is highest.
• An offset account. Balances held in a full offset reduce the balance interest is charged on, dollar for dollar, without being locked into the loan. At 6.29%, $20,000 sitting in an offset saves about $105 of interest a month while remaining available to withdraw.
• Refinancing to a fresh 30-year term. The most common expensive mistake. A lower rate on a new 30-year term can reduce the monthly figure while adding six figures of lifetime interest, because the years already paid down are reset. Ask for term-for-term pricing on your remaining term.
• Coming off a fixed rate. Fixed loans revert to a variable rate that is usually well above new-customer pricing. The repayment step at revert is often larger than any single rate decision.