How to Calculate Your Home Loan Borrowing Power

Your borrowing capacity depends on how lenders assess your income against your expenses and debts.

Most lenders in Australia use a serviceability calculator that takes your gross income, subtracts your living expenses and existing debt commitments, then applies a buffer to see whether you can service a loan at rates higher than today's offerings. The result is the maximum amount they'll lend you. That figure changes depending on which lender you approach, what your income looks like, and how much deposit you've saved.

For medical professionals and residents working at Westmead Hospital or Parramatta CBD, your borrowing capacity often sits higher than standard employment income because lenders recognise the stability and earning trajectory in healthcare roles. Some lenders offer specific packages for doctors that waive Lenders Mortgage Insurance (LMI) even with smaller deposits, which can increase how much you can borrow without needing to save a full 20% deposit.

How Lenders Calculate What You Can Borrow

Lenders multiply your net income by a serviceability ratio after accounting for your expenses and debts.

Consider a buyer who earns $120,000 per year working as a nurse at Westmead. The lender takes that gross income, deducts tax, then subtracts monthly expenses like rent, groceries, transport, and any credit card limits or personal loan repayments. They then assess whether the remaining amount can service a loan at an interest rate that's typically 3% higher than the current variable rate. If the loan still fits within that buffer, you're approved. If it doesn't, the lender reduces the loan amount until it does.

This is why two people earning the same income can get different borrowing amounts. Someone with a $15,000 credit card limit and a $400 monthly car loan will borrow less than someone with no debts, even if they never use the credit card. Lenders assess the limit, not the balance.

The Household Expenditure Measure and Living Costs

Your living expenses are either declared or calculated using the Household Expenditure Measure.

If you're currently renting in Parramatta and declare $2,500 per month in living costs, most lenders will compare that figure against the HEM benchmark for your household size and location. If your declared expenses fall below the HEM figure, they'll use the higher amount. This catches people off guard when they assume declaring lower expenses will help them borrow more. It doesn't. The lender applies whichever figure is higher to ensure you can genuinely afford the repayments.

For a single person in Parramatta, the HEM figure sits around $2,200 to $2,400 per month depending on the lender. For a couple, it's closer to $3,200 to $3,500. If you're supporting children, the figure increases further. This is one reason why a dual-income household without dependents can often stretch their borrowing capacity further than a single high earner with the same combined income.

Debt Commitments and Credit Limits

Every dollar of debt reduces your borrowing power by roughly $5 to $6 in loan capacity.

If you're carrying a $10,000 personal loan, that might reduce your borrowing capacity by $50,000 to $60,000 depending on the lender's calculation. Credit card limits hit harder. A $20,000 combined credit card limit can reduce your borrowing power by $100,000 or more, even if you pay the balance in full every month. Lenders assume you could max out the card tomorrow, so they factor the full limit into their serviceability assessment.

In our experience working with buyers around Parramatta, paying down or closing unused credit accounts before applying for a home loan is one of the most effective ways to increase how much you can borrow. If you're six months out from applying, start reducing those limits now.

How Deposit Size Affects Borrowing Power

A larger deposit doesn't increase how much you can borrow, but it does increase how much you can spend.

If a lender approves you for a $600,000 loan and you have a $100,000 deposit, you can purchase a property worth $700,000. If you only have a $50,000 deposit, you're looking at properties around $650,000. The deposit changes the purchase price, not the loan amount. However, a deposit below 20% means you'll pay LMI, which gets added to your loan and can reduce how much you have left to borrow. For medical professionals, some lenders waive LMI on loans up to 90% or even 95% of the property value, which means your deposit stretches further without the additional insurance cost.

Property Prices and Loan Amounts in Parramatta

Parramatta's median unit price sits around $650,000, while houses typically start closer to $1.2 million.

If you're looking at a two-bedroom apartment near Church Street or the Parramatta River foreshore, you're likely looking at properties between $600,000 and $750,000. To borrow $600,000 with a 10% deposit, you'd need a household income of roughly $140,000 to $160,000, assuming minimal debts and standard living expenses. If you're aiming for a house in the Harris Park or Westmead area, you'll need closer to $1 million in borrowing capacity, which typically requires a combined household income above $220,000 or a single high income with low commitments.

Medical residents and registrars often find themselves in a position where their current income doesn't support the borrowing capacity they need, but their future income will. Some lenders allow you to include your expected salary increase within the next 12 months if you can provide evidence of your contract or progression pathway. This can bridge the gap between what you earn now and what you'll need to service the loan.

Using an Offset Account to Build Equity Faster

An offset account linked to your home loan reduces the interest you pay without changing your repayment amount.

If you borrow $600,000 on a variable rate and keep $30,000 in your offset, you only pay interest on $570,000. Your repayments stay the same, but more of each payment goes toward reducing the principal. Over time, this builds equity faster and shortens your loan term. For buyers who receive irregular income, like shift allowances or overtime, an offset gives you flexibility to park extra funds without locking them into the loan permanently.

Fixed Rate vs Variable Rate Borrowing

Your borrowing capacity can differ depending on whether you choose a fixed or variable rate.

Some lenders assess fixed rate loans using the actual fixed rate plus a smaller buffer, while others apply the same 3% buffer regardless. If current variable rates sit around 6.5% and fixed rates are closer to 6%, a lender that uses the actual rate may approve a slightly higher loan amount on a fixed product. That said, fixing your rate locks you in for the term, and break costs apply if you need to refinance or sell early. A split loan can give you some rate certainty while keeping part of your loan flexible.

What to Do Before You Apply

Get a pre-approval before you start looking at properties.

Pre-approval tells you exactly how much you can borrow and gives you confidence when making an offer. It also highlights any issues with your application early, so you can address them before you find a property you want to buy. If your borrowing capacity comes back lower than expected, you'll have time to reduce debts, increase your deposit, or explore lenders with more flexible serviceability policies. We regularly see buyers who assume they can borrow a certain amount, only to find out their credit card limits or car loan have reduced their capacity by $100,000 or more.

Call one of our team or book an appointment at a time that works for you. We'll run the numbers, compare your options across lenders, and show you exactly where you stand before you start looking.

Frequently Asked Questions