About the Mortgage Repayment Calculator
A mortgage repayment calculator Australia helps home buyers and investors estimate their monthly home loan repayments based on loan amount, interest rate, and loan term. This essential financial planning tool allows Australian borrowers to compare loan options and understand how interest rate changes affect their budget. ASIC recommends using repayment calculators before committing to a home loan.
What is the Mortgage Repayment Calculator?
This calculator estimates the principal and interest (P&I) or interest-only (IO) repayments for a home loan. It takes the loan amount, annual interest rate, and loan term in years, then calculates the monthly repayment amount using the standard amortisation formula. For P&I loans, each payment covers both the interest charge and a portion of the principal, so the loan balance decreases over time. For IO loans, payments cover only interest for a set period, typically 1 to 5 years, after which the loan reverts to P&I. The calculator also allows you to see the impact of extra repayments, showing how additional contributions reduce the loan term and total interest paid. It supports comparisons across different loan structures including fixed-rate, variable-rate, and split loans. Australian borrowers use this tool to assess whether they can afford a property, compare lender offers, and plan for interest rate rises. The calculator also shows total interest payable over the full loan term, providing a complete picture of the true cost of borrowing. Rates and thresholds change every year, so rerun the Mortgage Repayment Calculator whenever your inputs change.
How to Use This Calculator
- 1Enter the loan amount: Input the total amount you plan to borrow from your lender.
- 2Enter the annual interest rate: Input the current interest rate offered by your lender as a percentage.
- 3Enter the loan term: Input the number of years over which you will repay the loan, typically 25 or 30 years.
- 4Select repayment type: Choose between principal and interest or interest-only repayments.
- 5Enter extra repayments (optional): Input any additional monthly amount you plan to pay to reduce the loan faster.
- 6Review your repayment schedule: The calculator shows monthly repayment amount, total interest payable, and loan term with extra repayments.
Worked Australian Example
Practical Example
Sarah is buying her first home in Newcastle, NSW for $620,000. She has a $124,000 deposit and needs a loan of $496,000 at 6.3% interest over 30 years with P&I repayments. Using the calculator, she enters $496,000 as the loan amount, 6.3% as the interest rate, 30 years as the term, and selects P&I. The calculator shows a monthly repayment of $3,068, with total interest over the loan term of approximately $608,480. Sarah decides to pay an extra $300 per month. With this extra repayment, the calculator shows her loan will be paid off in 24.5 years instead of 30, saving $97,200 in total interest. She also tests a scenario where the interest rate rises to 7.3%, increasing her monthly payment to $3,396. This helps her stress-test her budget. Sarah now knows she can comfortably afford the loan even with some rate increases, and she proceeds with pre-approval.
How Our Mortgage Repayment Calculator Works
Your repayment is calculated with the standard amortising loan formula that every Australian lender uses for principal-and-interest loans: **Repayment = P × r × (1 + r)^n ÷ ((1 + r)^n − 1)** where **P** is the loan amount, **r** is the periodic interest rate (annual rate ÷ number of payments per year), and **n** is the total number of payments over the loan term. In plain English, the calculator works out the fixed periodic amount that fully clears the loan — principal plus interest — by the end of the term. Two things follow from this formula: - **Early payments are mostly interest.** Because interest is charged on the outstanding balance, the interest portion is largest at the start and shrinks as the balance falls, while the principal portion grows. - **Frequency matters.** Paying fortnightly rather than monthly means you make the equivalent of 13 monthly payments a year instead of 12, cutting both the term and total interest. The calculator also totals the interest paid over the life of the loan (total repayments minus the amount borrowed). It models a constant interest rate, so on a variable loan your real repayments will move with rate changes.
When to Use This Calculator
Use this before and during a property purchase. **When house-hunting**, test different loan sizes to find a repayment you can comfortably service, and check the total-interest figure — not just the monthly amount — since a longer term lowers repayments but raises lifetime interest. **Before you lock in a rate**, compare how a 0.25–0.50% difference changes repayments, which shows the real value of negotiating. **After settlement**, use it to see how switching to fortnightly payments or adding extra repayments shortens the loan. It's also useful when a variable rate moves: re-run it at the new rate to plan your budget. Remember to add rates, insurance and (for units) strata to build a full ownership-cost picture.
Common Mortgage Repayment Calculator Questions
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