Proven Tips to Calculate Your Borrowing Capacity

How Lenders Calculate What You Can Borrow

Lenders calculate your borrowing capacity by assessing your income, expenses, existing debts, and the loan-to-value ratio, then testing your ability to service the loan at an interest rate at least 3 percentage points above the actual rate. APRA requires all banks and regulated lenders to apply this buffer to new borrowers, which means a loan priced at 6.2% variable would be assessed at 9.2% or higher. The buffer exists to protect borrowers from rate rises, but it also constrains how much you can access upfront.

Consider a buyer in Hornsby earning $95,000 who applies for a variable rate loan with offset. The lender prices the loan at 6.1%, but assesses serviceability at 9.1%. Monthly repayments on a $600,000 loan at 9.1% over 30 years come to roughly $4,860. If the lender applies a household expense measure of around $2,400 and the buyer has a car loan with $450 monthly repayments, the lender calculates net surplus income each month. If surplus income is insufficient to cover the assessed repayment, the loan amount is reduced until the buffer test passes. This is why two applicants with identical salaries can be approved for different amounts depending on their cost structure and debt position.

Income Assessment and the Role of Secondary Earnings

Most lenders apply 100% of base salary or wage income when calculating your capacity, but treat bonuses, overtime, and commission income differently. Some lenders will accept 80% of the previous two years' average for bonus and overtime, while others require a longer track record or cap the amount they will include. Self-employed applicants typically need two years of tax returns showing consistent or growing profit, though some lenders assess one year for established businesses in low-risk industries. Rental income from investment properties is usually shaded by 20% to 30% to account for vacancy and maintenance.

In our experience, buyers who structure their income documentation early tend to avoid delays. If you are earning additional income through a side business or short-term contract work, speak to a mortgage broker in Hornsby before submitting your application, because policy varies across lenders and the treatment of that income can swing your approval by $50,000 or more.

Debt Obligations and the DTI Limit

From 1 February 2026, APRA activated a debt-to-income lending limit requiring banks to restrict new lending at a DTI of six times or more to no more than 20% of new owner-occupier loans and 20% of new investor loans each quarter. If your total borrowings, including the new home loan, exceed six times your gross household income, the lender may still approve the loan, but those approvals are rationed. Non-bank lenders are not subject to this cap, which opens up alternative pathways if your application sits above the threshold.

A Hornsby household earning $140,000 combined who wants to borrow $900,000 sits at a DTI of 6.4. If the household has no other debt and meets all other serviceability criteria, approval is still possible, but the lender's quarterly allocation may delay the application or trigger a referral to a specialist credit team. The alternative is to either reduce the loan amount to $840,000, bringing the DTI to exactly 6.0, or approach a non-ADI lender who applies their own risk settings without the quarterly constraint. Both options require a clear view of your financial position and the trade-offs involved.

Living Expenses and the Household Expenditure Measure

Lenders assess your monthly living expenses using either your declared expenses or a benchmark household expenditure measure, whichever is higher. The benchmark is scaled to household income and applies across all major banks. If you declare $2,000 in monthly expenses but the benchmark for your income bracket is $2,600, the lender uses $2,600. This often surprises applicants who budget carefully, because the lender applies a floor regardless of actual spending.

Buyers who reduce recurring subscription costs, consolidate personal debt, or close unused credit card accounts before applying can increase their assessed capacity. A credit card with a $15,000 limit costs you roughly $450 per month in assumed repayments at 3% of the limit, even if the balance is zero. Closing that card before you lodge your home loan application can lift your borrowing capacity by $40,000 to $60,000 depending on your income and the lender's serviceability model.

Property Type, Location, and LVR Constraints

Lenders adjust risk settings based on property type, postcode, and loan-to-value ratio. A standard three-bedroom house in Hornsby on a registered title will attract lower risk weighting than a studio apartment in an oversupplied precinct or a property on a high-density development site. Postcode-level adjustments are common, particularly for locations with high concentrations of investor stock or limited infrastructure.

LVR also determines whether lenders mortgage insurance applies. At 80% LVR or below, LMI is not required. Above 80%, the premium is calculated on a sliding scale and can add $10,000 to $30,000 or more to your upfront costs depending on loan size. If you are purchasing in Hornsby with a smaller deposit, the Australian Government 5% Deposit Scheme allows eligible first home buyers to borrow up to 95% LVR without paying LMI, provided the property price sits within the applicable cap of $1,500,000 for capital cities and regional centres in NSW.

How Rate Type Influences Your Approval Amount

Fixed rate, variable rate, and split rate loans are all assessed using the same serviceability buffer, but the rate you lock in affects your actual repayment once the loan settles. A fixed rate priced at 5.8% over three years will be assessed at 8.8% for serviceability, but your real monthly repayment will be calculated at 5.8%. Buyers sometimes assume a fixed rate increases their borrowing capacity because the rate is lower, but the buffer applies equally across all rate types.

If you are comparing fixed and variable rate structures, model both scenarios using your lender's serviceability rate, not the advertised product rate. Your approval amount will not change, but your repayment structure and exposure to future rate movements will. Borrowers who split their loan between fixed and variable typically do so to lock in part of their repayment while retaining flexibility on the remainder, rather than to increase how much they can borrow upfront.

Pre-Approval and Why the Number Changes

A home loan pre-approval gives you a conditional borrowing limit based on your income and liabilities at the time of assessment, but it is not locked in. If you take on new debt, change jobs, or if the lender's policy is updated before you submit a full application, your approved amount can move. Pre-approvals are typically valid for 90 days, though some lenders extend this to six months depending on the product.

Buyers who secure pre-approval before attending auctions in Hornsby or surrounding suburbs should avoid applying for new credit during the validity period. Even a small personal loan or buy-now-pay-later account can reduce your capacity by enough to push you below the contract price. If your circumstances change, speak to your broker before signing a contract, because the final approval will reflect your position at settlement, not at pre-approval.

Using Offset Accounts to Manage Surplus Income

An offset account linked to your variable rate home loan reduces the interest charged on your loan balance without affecting your contractual repayment. If you hold $20,000 in offset against a $600,000 loan, you pay interest only on $580,000, but your repayment remains calculated on the full $600,000. The difference is applied directly to your principal, shortening your loan term and reducing total interest paid.

Borrowers in Hornsby who receive irregular income, such as annual bonuses or rental payments, often use offset accounts to park surplus cash while retaining access if needed. This strategy does not increase your initial borrowing capacity, but it improves your loan performance over time and positions you to refinance or increase your limit later without needing to demonstrate additional savings.

Call one of our team or book an appointment at a time that works for you to discuss your borrowing capacity and the loan structure that aligns with your circumstances in Hornsby and the surrounding area.

Frequently Asked Questions