Mortgage Calculator

These calculations are illustrative estimates based on the inputs you enter. They don't account for your full financial picture, lender-specific policies, or changes in interest rates over time. For advice tailored to your circumstances, speak with the team at Hunter Galloway.

How to use this mortgage repayment calculator

Getting a number out of this calculator takes about thirty seconds. Punch in your loan amount, your interest rate, and your loan term, then choose whether you want to see monthly, fortnightly, or weekly repayments. Hit calculate and you'll get an estimated repayment figure straight away.

A few things worth knowing before you start:

• Loan amount: Enter the amount you're borrowing, not the purchase price of the property. If you're buying a $700,000 home with a $140,000 deposit, your loan amount is $560,000.
• Interest rate: Use the rate you've been quoted, or a rate you're researching. Not sure what rate to use? Start with the current variable rate ballpark and then try a few different figures to see how sensitive your repayments are to rate movements.
• Loan term: Most home loans in Australia run for 25 or 30 years. A longer term means lower monthly repayments but more interest paid overall.
• Repayment type: Select principal and interest (P&I) to pay down the loan over time, or interest-only (IO) to see what you'd pay if you're only covering the interest charge each period.

Once you've got a figure, try adjusting the numbers. Even small changes, like half a percent on the interest rate or knocking five years off the term, can shift your repayments significantly. Playing around with the calculator is one of the most useful things you can do before you start talking to lenders.

How mortgage repayments are actually calculated

Your repayment is calculated using a standard amortisation formula. Put simply, each repayment covers that period's interest charge first, and whatever's left over reduces the loan balance (the principal). Early in your loan, most of each repayment goes to interest. As the balance falls, more of each payment chips away at the principal, which is why the last few years of a 30-year mortgage can feel like you're making real progress.

The formula itself takes three inputs: the loan balance, the interest rate divided into the number of repayment periods in a year, and the total number of repayments over the life of the loan. The calculator handles all of that automatically.

One thing that surprises some borrowers is that if you switch to fortnightly or weekly repayments instead of monthly, you can end up making the equivalent of one extra monthly repayment per year. That extra money goes straight to principal reduction, which can shave years off your loan and save a meaningful amount in interest.

What affects how much you repay each month?

Interest rate

Your interest rate has the biggest impact of all. A rate that's one percentage point higher on a $600,000 loan can add hundreds of dollars to your monthly repayment. This is why comparison matters, and why a small rate difference across a 30-year loan adds up to tens of thousands of dollars in total interest.

Loan size

Larger loan, larger repayment. Your deposit size directly drives this. Borrowers putting down at least 20% of the property value avoid Lenders Mortgage Insurance (LMI), which is a one-off cost that can run into the thousands and is often added to the loan balance, pushing repayments higher.

LVR and LMI

Your Loan to Value Ratio (LVR) is the loan amount expressed as a percentage of the property's value. Borrow more than 80% of the purchase price (that is, put down less than 20% deposit) and most lenders will require you to pay LMI. This protects the lender, not you, if you default. Our LMI calculator and LVR calculator can help you understand the numbers before you commit. There are also government schemes like the Australian Government 5% Deposit Scheme (formerly the First Home Guarantee) that let eligible first home buyers purchase with as little as a 5% deposit without paying LMI, which is worth exploring if you're earlier in your savings journey.

Loan term

A 30-year loan has lower monthly repayments than a 25-year loan on the same amount and rate, but you'll pay considerably more interest over the life of the loan. A shorter term means more paid each month and less interest overall. It's a trade-off between cash flow now and total cost over time.

Principal & interest versus interest-only

With a principal and interest (P&I) loan, every repayment reduces your balance. With an interest-only (IO) loan, you're only covering the interest charge, so the loan balance doesn't shrink at all during the IO period. Interest-only repayments are lower in the short term, but when the IO period ends and the loan reverts to P&I, repayments jump because you now have less time to pay off the same balance. IO loans are common for investment properties for cash flow and tax reasons, but they carry risks and aren't suited to everyone.

Fixed versus variable: which rate does the calculator use?

The calculator works with whatever rate you enter, fixed or variable. The difference matters a lot in practice.

A variable rate moves up and down with the lender's decisions, which are influenced by (but not identical to) the Reserve Bank of Australia's cash rate. Your repayments change when the rate changes. Variable loans typically offer more flexibility, with features like offset accounts, unlimited extra repayments, and the ability to refinance without break costs.

A fixed rate locks in your interest rate for a set period, usually one to five years. Your repayments don't change during that time, which makes budgeting easier. The trade-off is less flexibility, because extra repayments are often capped, offset accounts may not be available, and breaking a fixed rate early can attract significant costs.

Many borrowers choose a split loan (part fixed, part variable) to get some payment certainty while keeping access to offset and extra repayment features. There's no universally right answer. It depends on your circumstances, your risk appetite, and where rates are heading, which nobody knows for certain.

How lenders assess what you can actually borrow

What this calculator tells you and what a lender will actually approve you for can be quite different things. Lenders don't just look at whether you can afford the repayment at today's rate. They stress-test your application.

The key mechanism is the serviceability buffer, currently around 3% above the actual loan rate. So if you're applying for a loan at 6%, the lender assesses whether you could still afford repayments at roughly 9%. This is a regulatory requirement set by APRA and applies to essentially all lenders in Australia. It exists to make sure borrowers aren't stretched to the point where a rate rise or income disruption tips them into hardship.

Lenders also look at your income, employment type, existing debts, credit history, and living expenses. Many use what's called the Household Expenditure Measure (HEM) as a benchmark for living costs, and they'll use whichever is higher: your actual declared expenses or the HEM benchmark for your situation. This means that even if you're a disciplined saver, the lender may assess your expenses higher than what you actually spend.

The takeaway is that your actual borrowing capacity is worth getting assessed properly before you fall in love with a property. Our home loans team can run a proper assessment of your situation across multiple lenders, not just one.

Practical ways to lower your repayments (or pay off faster)

Use an offset account

An offset account is a transaction account linked to your home loan. The balance in the offset reduces the principal on which interest is calculated. If you have a $500,000 loan and $50,000 sitting in your offset, you're only charged interest on $450,000. Your repayment stays the same, but more of it hits the principal each period, which means you pay the loan off sooner. Offset accounts are generally only available on variable rate loans.

Make extra repayments

Even small additional repayments make a meaningful difference over time. An extra $200 a fortnight on a $600,000 loan can cut years off your term. Use our extra repayment calculator to see what additional payments could do for your specific loan.

Refinance when it makes sense

If your rate hasn't been reviewed in the past couple of years, there's a reasonable chance you're paying more than you need to. Lenders often offer better rates to new customers than to existing ones. Refinancing can mean a lower rate, better features, or both, but it's important to factor in any exit fees, application fees, and the time it takes to recoup those costs through interest savings.

Shorten the term (if your cash flow allows)

Refinancing to a shorter term, say from 30 years to 25, will increase your repayments but dramatically reduce the total interest you pay. Use the deposit calculator to see how your savings are tracking, and have a conversation with a broker about whether a shorter term fits your overall financial position.

Switch to fortnightly repayments

It sounds minor, but switching from monthly to fortnightly repayments means you make 26 half-repayments per year, the equivalent of 13 monthly repayments instead of 12. That thirteenth repayment goes straight to principal every year, which compounds over time to a meaningful reduction in interest paid.

Common mistakes to avoid

• Using today's rate as a fixed ceiling. Rates move. Before committing to a loan, make sure you've stress-tested your repayments at a rate a few percentage points higher, and that you're comfortable with the higher figure.
• Forgetting the upfront costs. Stamp duty, conveyancing fees, building inspections, and (if your LVR is above 80%) LMI can add tens of thousands of dollars to your purchase. Budget for these on top of your deposit.
• Comparing loans on rate alone. A slightly higher rate with an offset account and unlimited extra repayments can cost you less over the life of the loan than a rock-bottom rate with no features and break costs baked in.
• Borrowing to your absolute limit. Just because a lender will approve a certain amount doesn't mean borrowing that much is wise. Leave yourself a buffer for rate rises, unexpected costs, and life events.
• Not getting pre-approval before inspecting property. Knowing what you can actually borrow before you start making offers puts you in a much stronger position, and saves you the heartbreak of missing out on a property because your finance wasn't sorted.

Your repayment is calculated using an amortisation formula that accounts for three things: the loan balance, the interest rate (divided into monthly or fortnightly periods), and the total number of repayments over the loan term. Each repayment covers that period's interest first, with the remainder reducing your principal. Early in the loan, most of each repayment is interest. Over time, as your balance falls, the split shifts so that more of each payment reduces the loan itself.

Most lenders require a minimum 5% deposit, though you'll typically need at least 20% to avoid paying Lenders Mortgage Insurance (LMI). Some lenders accept lower deposits, and government schemes like the Australian Government 5% Deposit Scheme (formerly the First Home Guarantee) allow eligible first home buyers to purchase with a 5% deposit without LMI (property price limits still apply). The more deposit you have, the lower your LVR, the less you borrow, and the lower your repayments. Use our deposit calculator to work out how long it will take to reach your target.

Fortnightly repayments are generally the most popular option for a good reason: because there are 26 fortnights in a year (not 24), you end up making one extra monthly repayment's worth of payments each year. That extra amount goes directly to principal and can shave years off a 30-year loan while saving a significant amount in interest. Weekly repayments have a similar effect. Monthly repayments are the simplest but typically cost more in interest over the full loan term. The right frequency also depends on when you get paid, because aligning your repayment day with your pay day makes budgeting easier.

With principal and interest (P&I) repayments, each payment reduces your loan balance. You're building equity from day one and will have paid off the loan entirely at the end of the term. With interest-only (IO) repayments, you're only covering the interest charge, so your loan balance doesn't decrease at all during the IO period. IO repayments are lower in the short term, but when the IO period ends (typically after 1 to 5 years), your repayments jump because you have less time to repay the same principal. IO loans are sometimes used for investment properties for cash flow management, but they're generally not recommended for owner-occupiers unless there's a specific financial strategy in place.

Use the rate you've been quoted by a lender, or a rate you're researching as a benchmark. If you don't have a specific rate yet, it's worth speaking with a broker who can give you a realistic indication based on your situation before you start crunching numbers. We'd also suggest running the calculator at a rate 1% to 2% higher than you expect to use. This gives you a sense of how your repayments would look if rates rise, and whether you'd still be comfortable. That stress-test is something lenders do automatically (at around 3% above the actual rate), so it's worth doing it yourself too.

Borrowing capacity depends on your income (including its stability and type), your existing debts and financial commitments, your living expenses, your deposit, and the lender's own policies. Lenders assess serviceability using a buffer of roughly 3% above the actual loan rate, so if you're borrowing at 6%, they'll check whether you can afford repayments at around 9%. The calculator can show you what a given loan amount costs to service, but your actual maximum borrowing capacity requires a proper assessment. The team at Hunter Galloway can assess your capacity across a wide panel of lenders rather than just one, which often makes a meaningful difference to the outcome.

If you're on a variable rate loan, your repayments will go up when interest rates rise. Lenders are required to notify you of any rate change, and your repayment will adjust accordingly. This is exactly why the serviceability buffer exists, because lenders want to know you can handle repayments at a higher rate before they approve your loan. If you're on a fixed rate, your repayments won't change during the fixed period regardless of what the market does. If you're concerned about rate exposure, an offset account or the option to make extra repayments can build a buffer that helps absorb future rate rises. It's worth modelling a few different rate scenarios in this calculator to understand your exposure before you commit.

No. This calculator shows estimated principal and interest repayments only. It doesn't factor in establishment fees, ongoing account fees, offset account fees, LMI premiums, or any other loan costs. These vary between lenders and loan products and can affect the true cost of your loan. When comparing loans, it's worth looking at the comparison rate (which includes most fees) as well as the advertised rate, and asking a broker to help you understand the full cost picture across different options.

Ready to take the next step?

A repayment calculator is a great starting point, but getting the right home loan takes more than a good number. It takes knowing which lenders suit your situation, understanding your actual borrowing capacity, and having someone in your corner who can negotiate on your behalf.

The independently owned team at Hunter Galloway has helped thousands of Brisbane borrowers find the right loan. With 2,400+ Google reviews and a 97% application approval rate, we know what it takes to get deals across the line.

Get started with a free assessment. We'll look at your full situation, run the numbers properly across our lender panel, and give you a clear picture of where you stand, with no obligation and no cost.

Call us on 1300 088 065 or book your free assessment online.