Using a Mortgage Repayment Calculator in Australia: A Step-by-Step Guide
Calculates principal and interest home loan repayments and total interest. This guide walks through what each input means, the formula behind the answer and a worked example using typical Australian figures. You can follow along in the free Mortgage Repayment Calculator.
Why it matters
Buying property in Australia involves a deposit, stamp duty, lender requirements such as the APRA serviceability buffer, and ongoing repayments that move with interest rates. Investors also weigh rental yield, negative gearing and capital gains tax.
What you need to enter
The calculator asks for 3 inputs. The table shows each one with the example value used later in this guide.
| Input | Example value |
|---|---|
| Loan amount ($) | 600000 |
| Interest rate (%) | 6.2 |
| Loan term (years) | 30 |
The formula
Repayment = P × r × (1 + r)^n ÷ ((1 + r)^n − 1), where r is the monthly rate and n the number of months.
Worked example
Entering the example values above gives these results:
| Result | Value |
|---|---|
| Monthly repayment | $3,674.81 |
| Fortnightly (monthly ÷ 2) | $1,837.41 |
| Total interest | $722,932.99 |
| Total repaid | $1,322,932.99 |
The headline figure is $3,674.81 (monthly repayment). Change any input in the calculator and every result updates instantly, so you can test different scenarios side by side.
How the monthly repayment changes with loan amount
The table below keeps every other input at the example value and moves only “Loan amount ($)” up and down by 10% and 20%. It shows how sensitive the monthly repayment is to that one figure.
| Loan amount ($) | Monthly repayment |
|---|---|
| 480,000 | $2,939.85 |
| 540,000 | $3,307.33 |
| 600,000 | $3,674.81 |
| 660,000 | $4,042.30 |
| 720,000 | $4,409.78 |
At 480,000 the result is $2,939.85; at 720,000 it is $4,409.78. If a small change in this input moves the answer a lot, it is worth double-checking that figure before you rely on the result.
A practical tip
Paying half your monthly repayment every fortnight makes 13 monthly payments a year and can cut years off the loan.
Keep going
Before relying on the number, read Common Mortgage Repayment Mistakes (and a Better Way). You might also find these guides useful:
- Borrowing Power Calculator Explained for Australians
- How the Stamp Duty Calculator (NSW) Works (With a Worked Example)
- Home Deposit Savings Calculator: Formula, Example and What the Result Means
Frequently asked questions
- Do these calculators match what my bank will say?
- Lenders use their own models, expense benchmarks and policies. Use these results to prepare, then speak to a lender or broker.
- Are stamp duty rates current?
- Duty thresholds are indexed or changed regularly. Always confirm with your state revenue office before relying on a figure.
- Is this financial advice?
- No. The calculators give general estimates only and don’t consider your objectives or financial situation.
Run your own numbers in the Mortgage Repayment Calculator.
Open the calculatorGeneral information only. Rates and thresholds change, usually on 1 July. Confirm current figures with the ATO or the relevant authority, and get personal advice for decisions about your situation.