BigBox Tools
Free online tool

Mortgage Calculator for real decisions

Buying a home is one of the biggest financial decisions you'll ever make, so it helps to go in with the numbers clearly in front of you. This mortgage calculator is built to give you a genuine, detailed picture of your loan — not just a monthly repayment figure, but the full story: total interest paid, how an offset account affects your outcome, what happens if rates rise, and how extra repayments can shave years off your loan.

No sign-up required. No data leaving your browser. Just the numbers.

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What can you calculate?
Monthly Repayments
Enter your home price, down payment, interest rate, and loan term to instantly see your monthly repayment and how it breaks down between principal and interest.
Total Interest Paid
It's easy to focus on the monthly number, but the total interest figure is where things get eye-opening. On a 30-year loan, you'll often pay close to the original purchase price again in interest alone.
Extra Repayments
Even a small amount added to your monthly repayment can make a surprising difference. See exactly how many months you'll save and how much interest you'll avoid by paying a little extra each month.
Offset Account Impact
Model your current offset balance, monthly contributions, and offset percentage to see exactly how much time and money you stand to save. One of the most powerful tools available to homeowners.
Rate Comparison
Wondering what happens to your repayments if interest rates go up by 1%? Use the rate comparison tool to see how your monthly payment and total cost shift when rates move.
Full Amortization Schedule
See a month-by-month or year-by-year breakdown of every payment across the life of your loan, showing exactly how much goes to principal versus interest at each stage.
Understanding your loan

Understanding LVR and LMI

Two terms that come up a lot in home lending are LVR (Loan-to-Value Ratio) and LMI (Lender's Mortgage Insurance). Your LVR is simply the size of your loan expressed as a percentage of the property's value. If you're buying a $500,000 home with a $100,000 deposit, your LVR is 80%.

Most lenders require LMI once your LVR exceeds 80% — meaning your deposit is less than 20% of the purchase price. LMI protects the lender (not you) in case you default on the loan, and it can add thousands of dollars to your costs. The calculator flags your LVR automatically so you always know where you stand.

Getting the most out of it

How to get the most out of this tool

Start by entering your real numbers — home price, expected deposit, and the interest rate you've been quoted or are currently paying. From there, experiment with the loan term. Dropping from 30 years to 25 years often increases your monthly repayment by less than you'd expect, while saving tens of thousands in interest.

If you have savings sitting in a bank account, model them as an offset balance and see the impact. Many people are surprised to find that $20,000–$50,000 in offset can shave two to four years off a standard 30-year mortgage.

Stress-test your budget. Use the rate comparison tool to check you can comfortably handle repayments if rates were to rise by 1–2% before committing to a loan. It's a simple step that can save a lot of stress down the track.

Export your results

Export your results to PDF

Once you've run your numbers, you can export a summary to PDF — useful for keeping a record, sharing with a partner, or taking into a meeting with your broker or lender.

One of the more powerful ways to use this feature is to run multiple scenarios and export each one separately. For example, you might model your loan at the standard repayment with no extras, then create a second scenario with an offset account added, and a third with extra monthly repayments on top of that. Exporting each scenario gives you a clear, side-by-side comparison you can refer back to — making it much easier to see which approach pays your loan off fastest and saves the most in interest over the life of the loan.

Use the report label field to name each export clearly so they're easy to tell apart.

Ready to run the numbers?

Free, instant, no sign-up

Open the calculator and start modelling your loan in seconds.

Open the Calculator