How Australian mortgage repayments work

A standard principal-and-interest calculation spreads the amount borrowed, plus interest charged on the declining balance, across the selected loan term. Early repayments contain a larger interest component because the outstanding balance is highest near the start. As the balance falls, more of each scheduled repayment goes towards principal.

The result is a mathematical repayment for the inputs entered. It is not necessarily the amount a lender will approve or debit. Lenders can use daily interest, particular rounding rules, minimum repayment settings and fee arrangements that create small differences from a general calculator.

Use the amount actually financed after the deposit, grants and upfront costs are accounted for. The interest rate should match the product and repayment type, not simply a market headline. A comparison rate can help compare certain fees, but it is calculated using a standard example and may not reproduce the cost of your own loan.

A useful mortgage plan includes more than one rate. Recalculate at the offered rate, then at rates one and two percentage points higher. Compare both the repayment and the amount of household income left after essential expenses. This does not predict future rates; it shows whether the plan has room to absorb change.

Also test a shorter and longer term. A longer term can reduce the scheduled repayment while increasing total interest. A shorter term can reduce interest but leave less monthly flexibility. The right comparison keeps the loan amount constant and changes one assumption at a time.

Ask the lender for a written repayment schedule and full fee disclosure, then compare those figures with the calculator. Confirm whether the quoted rate is fixed, variable or split, when it can change, and whether extra repayments are allowed without restriction. Treat a calculator as a scenario tool and the lender documentation as the product record.