Looking for a new home? If so, it's important to use a mortgage calculator to calculate how your home loan payments will fit into your budget. Our mortgage calculator makes it easy to find out what the monthly, fortnightly and weekly repayments will be for any loan.

Simply enter the loan details into the mortgage calculator below to see projected mortgage payments based on the type of home loan and your mortgage repayment frequency. By taking the time to understand what you can afford, you're one step closer to buying your dream home with confidence.


How do you calculate home loan interest?

Here's the general formula to calculate mortgage interest repayments:

Monthly Interest Payment = (Loan Amount × Monthly Interest Rate) / (1 - (1 + Monthly Interest Rate)^(-Total Number of Payments))

Let's break down the steps:

  1. Convert the Annual Interest Rate to Monthly: Divide the annual interest rate by 12 to get the monthly interest rate.

  2. Calculate Total Number of Payments: Multiply the number of years in the loan term by 12 (months) to get the total number of payments.

  3. Plug into the Formula: Insert the values into the formula mentioned above.

  4. Calculate Monthly Interest Payment: Use a calculator or spreadsheet software to perform the calculations.

  5. Calculate Total Repayments: Multiply the Monthly Interest Payment by the Total Number of Payments to get the total amount repaid over the loan term.

Or you could just use our mortgage calculator. You can also see the benefit in paying your mortgage fortnightly or weekly, versus monthly. Hint, paying fortnightly leads to nearly one extra month’s worth of mortgage payments through the year. However be sure to check the restrictions on your home loan, especially if it’s a fixed rate.

It's important to note that interest calculations can vary based on the compounding frequency. In Australia, most mortgages use monthly compounding, where interest is applied monthly to the remaining loan balance.

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LenderHome LoanInterest Rate Comparison Rate* Monthly Repayment Repayment type Rate Type Offset Redraw Ongoing Fees Upfront Fees LVR Lump Sum Repayment Additional Repayments Split Loan Option TagsFeaturesLinkCompare
6.04% p.a.
6.06% p.a.
Principal & Interest
  • No monthly or ongoing fees
  • Unlimited free redraw
  • No application fee
5.99% p.a.
5.90% p.a.
Principal & Interest
  • No application or ongoing fees. Annual rate discount
  • Unlimited redraws & additional repayments. LVR <80%
  • A low-rate variable home loan from a 100% online lender. Backed by the Commonwealth Bank.
Important Information and Comparison Rate Warning

Base criteria of: a $400,000 loan amount, variable, fixed, principal and interest (P&I) repayments. All products with a link to a product provider’s website have a commercial marketing relationship between us and these providers. These products may appear prominently and first within the search tables regardless of their attributes and may include products marked as promoted, featured or sponsored. The link to a product provider’s website will allow you to get more information or apply for the product. By de-selecting “Show online partners only” additional non-commercialised products may be displayed and re-sorted at the top of the table. For more information on how we’ve selected these “Sponsored”, “Featured” and “Promoted” products, the products we compare, how we make money, and other important information about our service, please click here.

Monthly repayment figures are estimates only, exclude fees and are based on the advertised rate for a 30 year term and for the loan amount entered. Actual repayments will depend on your individual circumstances and interest rate changes. For Interest only loans – the monthly repayment figure is applicable only for the interest only period. After the interest only period, your principal and interest repayments will be higher than these repayments. For Fixed rate loans – the monthly repayment is based on an interest rate that applies for an initial period only and will change when the interest rate reverts to the applicable variable rate.

The Comparison rate is based on a secured loan amount of $150,000 loan over 25 years. WARNING: These comparison rates apply only to the example or examples given. Different amounts and terms will result in different comparison rates. Costs such as redraw fees or early repayment fees together with costs savings such as fee waivers, are not included in the comparison rate but may influence the cost of the loan. Comparison rates are not calculated for revolving credit products. Rates correct as of . View disclaimer.

What determines home loan interest?

In Australia, mortgage interest plays a significant role in determining the overall cost of homeownership. Understanding how mortgage interest is calculated is crucial for individuals looking to purchase property and manage their finances effectively.

Mortgage interest calculation is influenced by several factors, including the loan amount, interest rate, loan term, and repayment frequency.

Banks determine interest rates based on various factors, including market conditions, the cost of funds, economic indicators, risk assessment, and the bank's own profitability goals.

It's also important to consider the fees on your home loan. They may not be reflected in the advertised rate, but a high comparison rate is usually indicative of high fees, which can add to the cost of a home loan.

If you're interested in seeing how extra payments or changes in interest rates could impact your mortgage, you can our extra repayments calculator to find out how you could shave months or even years off your home loan while saving a lot of money in interest.

The interest rate is a central factor in determining mortgage costs. Interest rates in Australia can be fixed or variable - some home loans are also split - with fixed rates remaining constant over a set period and variable rates subject to market fluctuations. The Reserve Bank of Australia's decisions regarding the official cash rate significantly influence variable interest rates offered by financial institutions.

Mortgage amortisation explained

This calculator employs the amortisation formula for calculating the monthly repayment, taking into account both the principal amount and the interest accrued. The formula uses the concept of an amortisation schedule, which outlines the gradual reduction of the loan balance over time.

Amortisation essentially refers to when: The borrower pays off the principal, the interest is calculated based on the remaining balance, leading to a decrease in the interest component of each payment.

On a $600,000 home loan over 30 years at an interest rate of 6.00% p.a. the amortisation schedule looks like the following table.

Of course, this doesn’t take into account a few things: You might refinance the home loan several times throughout its duration; interest rates fluctuate; and any interest-only payment periods you might have had.




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