How are Australian mortgage repayments calculated?

The tool uses the standard amortising loan formula. The monthly rate is the annual rate divided by 12, and the repayment is the loan amount times that rate divided by one minus (1 plus the monthly rate) to the negative number of months. Fortnightly repayments are shown as half the monthly figure paid 26 times a year, which pays the loan off faster.

What is LVR and why does it matter?

LVR is the Loan-to-Value Ratio — the loan divided by the property value. Above 80% LVR, lenders usually require Lenders Mortgage Insurance (LMI), an extra cost that protects the lender. Keeping LVR at or below 80% (a 20% deposit) avoids LMI.

What is the APRA 3% serviceability buffer?

APRA requires lenders to test whether you could still afford repayments if rates rose. Since 2021 the buffer has been 3 percentage points above the loan rate. The tool shows the repayment at this stressed rate so you can see what lenders assess you against.

Should I pay weekly, fortnightly or monthly?

Paying fortnightly using half the monthly amount means you make the equivalent of 13 monthly payments a year instead of 12, cutting years off the loan and saving interest. The tool shows the fortnightly figure so you can compare.

Does this include LMI, fees or offset accounts?

No. It flags when LMI is likely (LVR above 80%) but does not price it, and it ignores establishment fees, redraw and offset accounts. Treat the result as the core principal-and-interest estimate.

Australia Mortgage Calculator

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An Australia mortgage calculator that models a home loan the way Australian lenders actually assess it: your monthly and fortnightly repayments, your loan-to-value ratio (LVR), total interest over the term, and the repayment stress-tested with APRA’s 3% serviceability buffer. It also flags when Lenders Mortgage Insurance (LMI) is likely to apply.

How it works

The loan amount is the price minus your deposit. Repayments use the standard amortising formula:

M = P * r / (1 - (1 + r)^-n)

where P is the loan, r is the monthly rate (annual rate divided by 12) and n is the number of months. The fortnightly figure is shown as half the monthly repayment paid 26 times a year — a popular Australian strategy that squeezes in the equivalent of an extra monthly payment annually and shaves years off the loan.

Two lender rules shape the result:

LVR = loan / property value. Above 80%, lenders typically require LMI, so the tool flags it.
APRA serviceability buffer = the repayment recalculated at your rate + 3 percentage points. This is the figure lenders assess your capacity against, so it shows the safety margin built into approval.

Example and notes

Buy a 750,000 AUD home with a 150,000 AUD deposit at 6.0% over 30 years. The loan is 600,000 AUD, LVR is 80% (no LMI), and the monthly repayment is about 3,597 AUD. Assessed at the stressed 9.0% rate, the repayment lenders test you against rises to roughly 4,827 AUD a month.

This is a principal-and-interest estimate. It does not price LMI, establishment fees, offset accounts or redraw. All figures are calculated locally in your browser.