Online borrowing calculators are a useful starting point, but they rarely match what a lender will actually approve. That gap catches a lot of people off guard — not because the calculators are wrong, exactly, but because they’re working from a simplified version of what lenders actually assess.
Here’s a clearer picture of how borrowing capacity is genuinely calculated, and why the number can shift more than people expect. If you’re just starting out, it’s worth pairing this with our guide on how much deposit you actually need.
Borrowing Capacity Isn’t Just About Income
It’s tempting to think borrowing capacity is mostly a multiple of your income. In reality, lenders build a much fuller picture, and two people earning the same salary can have meaningfully different borrowing capacity depending on their expenses, debts and financial habits.
The main factors lenders assess include:
Income
Your base salary, plus how they treat additional income like overtime, bonuses, commissions or rental income — and this varies noticeably between lenders. Some will only count a portion of variable income, or require a longer history of it, before including it in full.
Living expenses
Lenders assess your actual declared expenses against a benchmark, often referred to as the Household Expenditure Measure (HEM), and generally use whichever figure is higher. Genuinely tracking your spending before applying can help you present an accurate (and sometimes more favourable) picture than guessing.
Existing debts and liabilities
This includes personal loans, car finance, buy-now-pay-later arrangements, and — importantly — the full available limit on credit cards, not just your current balance. A credit card with a $10,000 limit reduces your borrowing capacity based on that limit, even if you always pay it off in full each month.
HECS/HELP and other study debts
These are treated as an ongoing liability and factored into serviceability calculations, even though they don’t work quite like a typical loan.
The serviceability buffer
Lenders don’t just check whether you can afford a loan at today’s interest rate — they assess whether you could still service it at a notably higher rate, as a buffer against future rate rises. This buffer is a major reason borrowing capacity can look considerably lower than a simple “income times a multiple” estimate would suggest, and it’s also why capacity can shift when the broader rate environment changes.
Why Borrowing Capacity Estimates Vary So Much
If you’ve used more than one online calculator, or compared notes with a friend on a similar income, you may have noticed the numbers don’t line up. This happens because:
- Lenders apply different assessment rates and buffers
- Some lenders treat variable income, self-employment income or rental income more generously than others
- Living expense benchmarks and assumptions differ between lenders
- Your actual declared expenses (not just the benchmark) can pull the number down further, regardless of lender
This is exactly why a broker comparing your situation across multiple lenders — rather than relying on a single bank’s calculator — can surface a genuinely different (and sometimes considerably higher) outcome than the first number you’re given.
Why Did My Borrowing Capacity Go Down Since Last Time?
This is a common and reasonable question, particularly for anyone who checked their borrowing capacity a couple of years ago and is revisiting it now. A few things commonly move the number:
- Interest rate changes affect both the rate you’d actually pay and the serviceability buffer applied on top of it
- New debts — even a car loan or an increased credit card limit — reduce capacity
- Changes to income, including reduced overtime, a switch to part-time work, or a change in employment type
- Updated lender policy, since lenders periodically revise how conservatively they assess income, expenses or specific occupations
None of this means your situation is worse in absolute terms — it often just reflects a different lending environment than when you last checked.
How to Get a More Accurate Picture
Rather than relying on an online estimate, a more accurate borrowing capacity assessment typically involves:
- Providing actual payslips, bank statements and details of existing debts
- Being upfront about ongoing expenses, rather than underestimating them
- Understanding how your specific income type (PAYG, self-employed, casual, or a mix) is likely to be treated
- Comparing how different lenders on a panel would assess the same file, since policy differences can meaningfully change the outcome
How a Mortgage Broker Can Help
Borrowing capacity isn’t a single fixed number — it changes depending on which lender is assessing it and how your income and expenses are presented. Through our first home buyer loan service, a broker can:
- Model your borrowing capacity across multiple lenders, not just one
- Identify which lenders are likely to assess your specific income type most favourably
- Explain practical, honest ways to present your financial position accurately
- Flag anything (like an unused credit card limit) that might be quietly reducing your capacity
Ready for a Realistic Number?
Want a realistic picture of what you could borrow — not just a calculator estimate? Book a free borrowing capacity assessment with Money Tree Mortgage Brokers, or apply for pre-approval directly if you’re ready to move forward.
Book a Free Assessment
Frequently Asked Questions
Why is my borrowing capacity lower than an online calculator suggested?
Online calculators are usually simplified estimates. Actual lender assessments factor in your real expenses, existing debts, income type and a serviceability buffer, which typically produces a more conservative (and more accurate) figure.
Does a credit card I always pay off still affect my borrowing capacity?
Yes. Lenders generally assess your full available credit limit as a potential liability, regardless of your current balance or repayment habits.
Does overtime or bonus income count toward my borrowing capacity?
Often partially, depending on the lender and how consistent your history of that income is. Some lenders require a longer track record before including variable income in full.
What is the serviceability buffer?
It’s a margin lenders add on top of the actual interest rate when assessing whether you can afford a loan, designed to check you could still manage repayments if rates rose. This buffer is a major reason borrowing capacity estimates are more conservative than a simple income-based calculation.
Can my borrowing capacity change between lenders?
Yes, sometimes significantly. Each lender sets its own policies for assessing income, expenses and risk, which is why comparing across a broader panel can produce a different result than a single bank’s estimate.
Does HECS/HELP debt reduce how much I can borrow?
Yes, it’s generally treated as an ongoing liability in serviceability calculations, even though it isn’t a conventional loan.
