How are mortgage repayments calculated?

Each repayment covers the interest on the remaining balance plus a bit of principal. The repayment is set so the loan reaches zero exactly at the end of the term — the standard amortisation formula. Early on most of the payment is interest; later it's mostly principal.

Does paying fortnightly or weekly change anything?

This calculator works out a self-consistent repayment for whichever frequency you choose, with interest compounding at that frequency. Note that many lenders set fortnightly repayments at half the monthly amount — which means you pay a little extra each year and clear the loan sooner. To model that here, add an extra repayment.

How much do extra repayments save?

A lot, because every extra dollar comes straight off the principal and stops accruing interest for the rest of the loan. Enter an extra amount to see the interest saved and how many years it cuts off your loan.

Why is the total interest so large?

Over 25–30 years, interest compounds on a big balance, so total interest can rival the loan itself. That's why the interest rate, the term, and any extra repayments make such a difference — the calculator shows the total cost (loan + interest) so you can see it.

Mortgage Repayment Calculator — Australia

Work out your home-loan repayments. Enter your loan amount, interest rate and term to see your repayment per month, fortnight or week, the total interest over the loan, and how much extra repayments could save you.

Loan amount

Interest rate (per year)

Loan term (years)

Repayment frequency

Extra repayment (optional, per month)

Enter a loan amount, rate and term to see your repayments.

Assumptions. Standard principal & interest amortisation · constant interest rate for the life of the loan · interest compounds at the repayment frequency · excludes fees, offset and redraw · figures are rounded.

Disclaimer. This calculator provides a general estimate only and is not financial advice or a loan offer. Real loans can have fees, rate changes, offset/redraw and different repayment conventions, so your actual repayments may differ. Your figures are calculated in your browser and aren't sent anywhere. Confirm any figure with your lender.

Frequently asked questions

How are mortgage repayments calculated?: Each repayment covers the interest on the remaining balance plus a bit of principal. The repayment is set so the loan reaches zero exactly at the end of the term — the standard amortisation formula. Early on most of the payment is interest; later it's mostly principal.
Does paying fortnightly or weekly change anything?: This calculator works out a self-consistent repayment for whichever frequency you choose, with interest compounding at that frequency. Note that many lenders set fortnightly repayments at half the monthly amount — which means you pay a little extra each year and clear the loan sooner. To model that here, add an extra repayment.
How much do extra repayments save?: A lot, because every extra dollar comes straight off the principal and stops accruing interest for the rest of the loan. Enter an extra amount to see the interest saved and how many years it cuts off your loan.
Why is the total interest so large?: Over 25–30 years, interest compounds on a big balance, so total interest can rival the loan itself. That's why the interest rate, the term, and any extra repayments make such a difference — the calculator shows the total cost (loan + interest) so you can see it.