Mortgage Calculators Australia — Free Home Loan Tools
This article provides general information only and does not constitute financial advice. For advice tailored to your situation, consult a licensed financial adviser. Learn more.
Contents
Mortgage calculators help you understand the financial reality of a home loan before you commit to one. They turn abstract interest rate and loan term figures into concrete monthly repayment numbers, total interest costs, and borrowing limits that you can plan around.
These free calculators are built for the Australian market — using Australian tax rates, state-specific stamp duty formulas, and standard Australian home loan structures.
Which Calculator Do I Need?
| I want to… | Use this calculator |
|---|---|
| Estimate my monthly repayments | Mortgage Calculator |
| Find out how much I can borrow | Borrowing Power Calculator |
| Calculate stamp duty for my state | Stamp Duty Calculator |
| See if I’ll need to pay LMI | LMI Calculator |
| Compare renting to buying | Rent vs Buy Calculator |
| See how extra repayments save interest | Extra Repayments Calculator |
| See offset account savings | Offset Calculator |
| Calculate refinancing savings | Refinancing Calculator |
| Calculate my available equity | Home Equity Calculator |
| Find the true cost of a loan | Comparison Rate Calculator |
How Australian Home Loan Calculations Work
Principal and Interest Repayments
The standard Australian home loan uses a principal and interest (P&I) repayment structure. Each monthly repayment covers:
- Interest: Charged on the outstanding loan balance at the current interest rate
- Principal: The portion that reduces the loan balance
In the early years of a mortgage, the majority of each payment is interest. As the balance reduces, more of each payment goes to principal. This is why the total interest over a 30-year loan can exceed the original loan amount.
The formula for monthly repayments:
$$M = P imes rac{r(1+r)^n}{(1+r)^n - 1}$$
Where:
- $M$ = monthly repayment
- $P$ = loan principal
- $r$ = monthly interest rate (annual rate ÷ 12)
- $n$ = number of monthly payments (loan term in years × 12)
For a $700,000 loan at 6.5% over 30 years: monthly repayment ≈ $4,423, total interest over the life of the loan ≈ $892,280.
Borrowing Power
Your borrowing power is determined by your lender’s assessment of your capacity to repay the loan. Key inputs:
- Gross income (salary, rental income, other regular income)
- Existing commitments (credit card limits, car loans, HECS-HELP repayments, BNPL obligations)
- Living expenses (lenders use both your stated expenses and the Household Expenditure Measure as a benchmark)
- Interest rate buffer — APRA requires lenders to assess your ability to repay at the actual interest rate plus 3%
The 3% serviceability buffer means a loan at 6.5% is assessed as if the rate were 9.5%. This is a significant constraint that materially reduces borrowing capacity relative to what the repayment math alone might suggest.
Borrowing power is not the same as the amount you should borrow. Borrowing at maximum capacity leaves no buffer for rate increases, income interruptions, or unexpected expenses.
Stamp Duty
Stamp duty (land transfer duty) is a state and territory government tax on property transactions. It is one of the largest transaction costs in Australian property and varies significantly by state:
| State/Territory | Rate for $700,000 property (non-FHB) | First home buyer exemption |
|---|---|---|
| NSW | ~$26,000 | Duty waived for properties under $800,000 |
| VIC | ~$37,000 | Waived for properties under $600,000 |
| QLD | ~$17,750 | Waived for properties under $550,000 |
| WA | ~$22,000 | Concession for properties under $430,000 |
| SA | ~$29,500 | No exemption (first home grant available) |
| ACT | ~$21,600 | Concession scheme for eligible buyers |
| TAS | ~$25,800 | Concession for properties under $400,000 |
| NT | ~$24,400 | Concessions for properties under $650,000 |
Figures are approximate — use the stamp duty calculator for precise state-specific figures. First home buyer thresholds and concessions change with budget announcements.
Lenders Mortgage Insurance (LMI)
If your deposit is less than 20% of the property value (LVR above 80%), most lenders require you to pay LMI — a one-off premium that protects the lender (not you) if you default.
LMI is calculated as a percentage of the loan amount and varies by LVR and loan size. Approximate LMI costs:
| LVR | $500,000 loan | $700,000 loan | $1,000,000 loan |
|---|---|---|---|
| 85–90% | ~$8,500 | ~$12,500 | ~$18,000 |
| 90–95% | ~$17,000 | ~$25,000 | ~$36,000 |
LMI can be added to the loan (capitalised), meaning you pay interest on it for the life of the loan. First home buyers with deposits of 5–20% should factor LMI into their affordability calculation.
Some lenders offer LMI waivers for specific professions (doctors, lawyers, accountants) at higher LVRs. The First Home Guarantee scheme allows eligible first home buyers to buy with a 5% deposit without paying LMI (the government guarantees up to 15% of the loan).
The Offset Account Calculator
An offset account is a transaction account linked to your mortgage. The balance in the offset account reduces the loan balance on which interest is charged.
Example: A $700,000 mortgage with $50,000 in the offset account is charged interest on $650,000.
At 6.5%, the interest saving on $50,000 offset is approximately $3,250/year. Unlike a savings account earning interest (which is taxable), offset savings reduce your mortgage cost — effectively earning you the mortgage rate on your savings, tax-free.
The benefit of an offset account scales with how much you keep in it. Parking your salary and cash savings in the offset, then spending down from it through the month, maximises the average offset balance and interest saving.
Extra Repayments: How Much Do They Save?
Making extra repayments above the minimum reduces your loan balance faster, which reduces the total interest paid and shortens the loan term.
Example: On a $700,000 loan at 6.5% over 30 years, paying an extra $500/month:
- Reduces the loan term by approximately 6 years
- Saves approximately $190,000 in total interest
The earlier in the loan term you make extra repayments, the larger the saving — because interest is calculated on the outstanding balance.
Frequently Asked Questions
Are online mortgage calculators accurate? They provide reliable estimates based on your inputs. They cannot account for lender-specific assessment criteria, application fees, ongoing fees, or the impact of future rate changes. Use them to understand the order of magnitude of repayments and borrowing capacity, then speak with a lender or broker for a formal assessment.
What is a comparison rate? A comparison rate combines the interest rate and most fees and charges into a single rate to allow fair comparison between loans. It’s calculated on a standard $150,000 loan over 25 years. For larger loans, the comparison rate may be more meaningful as a relative indicator than as an absolute figure.
What does LVR mean? Loan-to-Value Ratio — the loan amount as a percentage of the property value. A $560,000 loan on an $800,000 property has an LVR of 70%. LVR below 80% avoids LMI and typically qualifies for better rates.
Repayment and Loan Calculators
- Mortgage Calculator — Monthly Repayments
- Borrowing Power Calculator — How Much Can I Borrow?
- Extra Repayments Calculator — How Much Will I Save?
- Offset Account Calculator
- Comparison Rate Calculator — True Cost of a Home Loan
Buying Costs Calculators
- Stamp Duty Calculator Australia (All States)
- Lenders Mortgage Insurance (LMI) Calculator
- Rent vs Buy Calculator Australia
Property and Investment Calculators
- Home Equity Calculator
- Refinancing Savings Calculator
- Negative Gearing Calculator Australia
- Rental Yield Calculator Australia
These calculators provide estimates only. Results assume constant interest rates and do not account for changes in income, living expenses, lender policy, or government charges. For advice tailored to your situation, speak with a licensed mortgage broker or financial adviser. You can find one through the ASIC financial advisers register or MoneySmart.
Making Sense of Mortgage Calculator Results
Understanding what the numbers mean — not just what they are — is as important as getting the calculation right.
Total interest vs monthly repayment: A lower monthly repayment is not always better. A 30-year loan vs a 25-year loan on the same amount at the same rate will have a lower monthly repayment for the 30-year loan — but significantly more total interest. Always check total interest paid over the life of the loan when comparing options.
Variable vs fixed rate calculations: Mortgage calculators use a single interest rate. Variable rate mortgages will have repayments that change when the rate changes. Fixed rate mortgages lock in a rate for a period (typically 1–5 years). A calculator at 6.5% accurately reflects a fixed loan at 6.5% — but a variable loan may change rate 3 times over the year.
Inflation and real cost: A $700,000 loan at 6.5% looks very large in nominal terms. In real (inflation-adjusted) terms, mortgage repayments become relatively cheaper over time as wages and prices rise, while the nominal repayment stays fixed (for fixed-rate loans) or moves with rates (for variable loans). This is one reason long-term mortgages are financially manageable despite large nominal totals.