Published 13 July 2026
Mortgage repayment calculator
Estimate your home loan repayments and the total interest over the life of the loan.
How are mortgage repayments calculated?
Every standard Australian home loan uses the same formula. It takes three numbers: the loan amount, the interest rate and the term. It turns them into one fixed repayment that clears the loan exactly on time. The repayment never changes, even though what is inside it does.
Why is the interest so large? Interest is charged on what is still owing. At the start the balance is big, so most of each repayment goes to interest. Near the end the balance is small, so most of each repayment clears the loan.
On the $700,000 example, total repayments come to $1,456,228: the $700,000 borrowed plus $756,228 of interest. The interest exceeds the amount borrowed. That is normal for a 30-year term at rates in the mid-fives, not a sign of a bad loan.
The formula works per repayment period, not per year. The rate per period is the annual rate divided by 100, then by the number of repayments in a year. That is 12 for monthly billing, 26 for fortnightly, 52 for weekly.
The chart with the results makes the mechanics visible. The remaining-balance line falls slowly at first and steeply at the end. Early repayments mostly pay interest on a large balance. Late repayments hit a small balance, so almost all of each one pays off the loan. The interest line mirrors it, climbing fastest in the early years and flattening towards the end. Extra repayments are powerful early and much weaker late for exactly this reason, whatever their size.
What does a $700,000 mortgage cost per month?
On the calculator's defaults, the repayment is $4,045 a month. This is the worked example, and every figure in this section describes it. Those defaults are a $700,000 loan at 5.66 per cent over 30 years. The amount is a round figure near the national average new owner-occupier loan. The rate is the RBA's published average for February 2026, covering new owner-occupier loans that pay principal and interest1.
Shortening the same loan to 25 years lifts the repayment to $4,366. That is $321 a month more. It also cuts total interest to $609,726. The five years removed are worth $146,501 in interest over the life of the loan. That trade, a higher repayment for a shorter term, is the biggest lever in the calculator. Rate moves of realistic size shift the totals by less.
How much does a rate change move repayments?
On the worked example's $700,000 loan over 30 years:
- A quarter of a percentage point moves the repayment by about $110 a month.
- Half a point moves it by about $224 a month, and $80,659 of interest over the full term.
Both figures are illustrative. They use the rates in the table below.
| Rate (p.a.) | Repayment per month | Total interest over the term |
|---|---|---|
| 5.16% | $3,826 | $677,539 |
| 5.41% | $3,935 | $716,631 |
| 5.66% | $4,045 | $756,228 |
| 5.91% | $4,156 | $796,317 |
| 6.16% | $4,269 | $836,887 |
Source · computed by the CheckRate amortisation engine on this page.
One thing worth noticing: rate rises cost more interest than same-sized cuts save. Interest builds on the balance still owing, so a higher rate keeps the balance higher for longer. The pattern holds at any loan size. The dollar figures scale with the amount borrowed.
Do fortnightly repayments save money?
Mostly no. Switching the worked example to fortnightly billing sets the payment at $1,866 a fortnight. Worked out properly, as this calculator does it, total interest changes by only $703 over the whole term. On its own, the switch is close to neutral: 26 smaller repayments a year pay down the same balance at the same annual rate.
The famous fortnightly trick is different. Paying half the monthly repayment every fortnight means 26 half-payments a year. Paired up, that is one extra month's repayment squeezed into every year. The extra money comes straight off the balance, and that is what shortens the loan. Lenders quoting big fortnightly savings usually mean that trick, not the recalculated payment shown here.
The saving comes from paying more, not from paying more often.
What are typical rates and loan sizes in 2026?
The average rate on new owner-occupier loans was 5.72 per cent in February 2026. Loans that pay principal and interest averaged 5.66 per cent. Loans already on lenders' books averaged 5.73 per cent1. Interest-only loans cost more. New ones to owner-occupiers averaged 6.40% in the same month. The averages span all lenders and products, fixed and variable alike. Real quotes sit both above and below them.
Loan sizes vary widely by state. The national average new owner-occupier loan reached $735,000 in the March quarter 2026. New South Wales led the states at $860,0002.
| State or territory | Average new owner-occupier loan |
|---|---|
| New South Wales | $860,000 |
| Queensland | $741,000 |
| Western Australia | $703,000 |
| Victoria | $675,000 |
| Australian Capital Territory | $665,000 |
| South Australia | $664,000 |
| Northern Territory | $536,000 |
| Tasmania | $521,000 |
Source · ABS Lending Indicators, March quarter 2026 release.
What does the calculator leave out?
The calculator leaves out three big things. All three push real costs above its figures.
- The rate is held constant. The calculator uses one rate for the whole term. Actual variable rates move with the market, and fixed rates expire into whatever follows them.
- Fees are excluded. Application fees and ongoing account fees sit outside the sums shown here. So does lenders mortgage insurance, the premium charged when the deposit is under a fifth of the purchase price.
- Repayment maths is not lending policy. The page shows what a loan costs to repay, not what a lender would approve. Approval depends on income, expenses and the buffers lenders add when they assess a loan. A repayment formula sees none of that.
Offset balances and extra repayments are not modelled either. Both work in the borrower's favour. Both shrink the balance that interest is charged on, so their effect grows over time. The assumptions block above the results lists each of these gaps and the reason for every default. The same list prints with the results.
The calculator also assumes every repayment pays principal and interest, from the first one. Interest-only loans work differently. During the interest-only period the balance does not fall at all. The loan then reverts to principal and interest and repays the full amount over a shorter remaining term. The RBA's February 2026 data shows new interest-only lending also carries a higher average rate. An interest-only calculator is the right tool for those loans. This page's figures describe standard amortising loans only.
Mortgage repayment questions
How much are the repayments on a $700,000 mortgage?
At 5.66 per cent over 30 years, a $700,000 principal-and-interest loan costs $4,045 a month (worked example). Total interest over the term is $756,228. The calculator above reworks both figures for any amount, rate or term.
How much home loan repayment is there per $100,000 borrowed?
About $578 a month per $100,000, at 5.66 per cent over 30 years (worked example). Repayments rise in proportion to the amount borrowed. Multiplying that figure gives a close estimate for any loan size at the same rate and term.
Do fortnightly repayments pay a mortgage off faster?
Not by themselves. A recalculated fortnightly instalment is $1,866 on the worked example. It changes total interest by only $703 across the term. The saving people describe comes from paying half the monthly amount each fortnight. That adds one extra monthly repayment a year, so it is really an extra-repayment strategy.
What does principal and interest mean?
The principal is the amount borrowed. Interest is the lender's charge on whatever balance is still owing. A principal-and-interest repayment covers the period's interest first, and the rest reduces the balance. That is why a fixed repayment clears the loan slowly at the start and quickly at the end. The alternative structure, interest-only, pays the charge without reducing the balance during its initial period.
What interest rate should the calculator use?
The calculator defaults to 5.66 per cent, the RBA's published average for new owner-occupier principal-and-interest loans in February 2026. Averages blend fixed, variable and differently priced products. A borrower with a rate quote or an existing loan gets more useful figures by entering that actual rate.
References
- RBA, Lenders' Interest Rates (Statistical Table F6) — housing rates, February 2026Reserve Bank of Australia
- Lending Indicators, March Quarter 2026, Table 24, cat. 5601.0Australian Bureau of Statistics