Calculator
House Affordability Calculator
House Affordability Calculator
Maximum Home Price
$419,798.09
Affordability Analysis
At a 30% total DTI ceiling, after $800 of existing debt you can carry a housing payment of about $2,450/month. With a $95,000 deposit at 6.3%, that supports a 25-year loan near $324,798.09 — a maximum price around $419,798.09. The back-end ratio is the binding constraint. Australian lenders also test repayments at roughly your rate plus a ~3% APRA serviceability buffer and watch the 6× income DTI line, so treat this figure as a starting point, not an approval. The $377,818.28 "comfortable" figure (10% under the max) leaves margin for repairs, moving costs, and rate rises — the gap between what a lender approves and what you can live with is where most mortgage-stress stories begin.
*Estimates using income, debts and an Australian-style P&I mortgage model. It does not perform full lender serviceability (credit history, HEM living expenses, LMI, APRA buffer testing, genuine savings) and should be treated as a planning starting point. Educational only, not lending advice.
What a Lender Approves vs. What You Can Comfortably Afford
House affordability is where aspiration collides with arithmetic, and the two numbers people conflate are different questions entirely. The first is the maximum a lender will approve — the ceiling set by your income, your existing debts, a debt-to-income ratio the bank deems safe (APRA pushes lenders to keep DTI above 6× income to a minority of loans), and the 3% buffer applied on top of the loan rate for serviceability testing. The second is the price you can actually live on — what remains after the mortgage, council rates, insurance, maintenance, and the life you still want to fund. Lenders are happy to approve you up to the limit of their risk model because their downside is capped and secured; your downside is thirty years of mortgage stress. This calculator computes both. The core mechanics work backward from a target total DTI. Take your monthly gross income, multiply by your chosen DTI ceiling, subtract the debts you already carry, and what remains is the maximum housing repayment you can service. From that payment — minus rates and insurance, which scale with price — the tool derives the maximum loan a 25-year mortgage supports at your rate, adds your deposit, and arrives at the maximum home price. It then also reports a 'comfortable' target set modestly below the ceiling. That gap between the approval number and the comfortable number is the whole point: it is where you keep room for super contributions, an emergency fund, repairs, and the flexibility that keeps a house from becoming a constraint. Affordability, properly computed, is not 'how much can I borrow' — it is 'how much can I borrow and still invest, save, and live.'
From a Repayment Budget to a Loan Amount to a Price
The calculation runs in three reverse-engineered steps. First, establish the repayment budget: monthly gross income × your target total DTI, minus existing monthly debt repayments, equals the maximum total housing payment you can carry. Second, split that payment. Council rates, water and building insurance are modelled as a percentage of the home price per year, so they grow with price; the remainder of the payment is what is left for principal and interest. Third, convert that P&I capacity into a loan. Using the standard amortisation annuity factor for a 25-year loan at your rate, the tool solves for the largest loan whose payment — plus the rates and insurance attributable to it — fits inside your budget. Adding the deposit yields the maximum home price. The comfortable target is simply that maximum discounted by a modest margin. Two subtleties explain why the numbers behave as they do. The rates-and-insurance drag means that as interest rates fall, more of your payment is freed up for principal, so the affordable price rises sharply on a rate drop — which is why RBA rate moves shift borrowing power more than most buyers expect. And because DTI uses gross income, the comfortable number is not a lender figure but a planning figure: it is meant to preserve investable cash flow after housing cost, which the approval number ignores. Running the calculator at a 30% DTI and then at 36% shows exactly how much house you gain by spending the bank's entire allowance — and the margin you surrender by doing so.
Expert Insights
Budget the Repayment, Not the Price
Buyers fixate on a target home price, but prices are the output, not the input — the input is the monthly repayment your budget can absorb while still funding everything else. Start from the repayment you can genuinely afford after super contributions, emergency savings, and daily living, then work backward to the price that produces it. Two households with identical incomes but different savings goals will have different comfortable repayments, and therefore different affordable prices, even though a broker quotes both the same approval. Anchoring on the repayment is what keeps the house from crowding out your portfolio; anchoring on the maximum approved price is what produces the mortgage-stress household.
The Comfortable Number Protects the Investment Plan
The most financially damaging affordability mistake is borrowing the maximum and spending it, because it consumes precisely the cash flow that would otherwise compound. A household that stretches to a 40%+ DTI to buy a larger home often forgoes the super salary sacrifice or emergency fund that the slightly smaller home would have preserved — and over twenty years the lost compounding can exceed the extra home equity. This calculator deliberately reports a comfortable target below the ceiling. Treat that gap not as money you could have borrowed but as the investable margin you are choosing to keep. A home purchased at the comfortable number appreciates just like the bigger one; the investor who kept the difference now owns the appreciation on both.
Remember the APRA Buffer: Banks Test You at Rate + 3%
Australian lenders must test your ability to repay at roughly your loan rate plus a 3% serviceability buffer. A loan quoted at 6.2% is assessed at about 9.2% — so the repayment the bank actually stress-tests is far higher than the one on the offer letter. Before submitting an offer, run this calculator at a rate a full point or two above your quote and confirm the repayment still fits your budget. If it only works at the quoted rate with stable income and no rate rises, you are buying fragility: the buyers who weather RBA hiking cycles are the ones who priced in the bad scenario before they bought, not after settlement set the terms in stone.
Actionable Tips
- 1
Budget Repayment Capacity Against a Rising Rate Environment
Use your real numbers and stress-test a rate at least 1–2 points above the current quote. Australian variable rates have moved through several full hiking and cutting cycles in recent years, and your repayment at 'rate + 2%' is the one that decides whether you end up in mortgage stress or still topping up your super. Run the calculator again at a target DTI of 30% rather than 36% — that single move is the cheapest insurance against house-poor years available, because it prices the buffer before the bank does.
- 2
Leave the Deposit Alone for Settlement and Reserves
The deposit input is not just the deposit — it must also cover stamp duty (commonly 4–6% of the price by state), conveyancing, lender fees, and a post-purchase reserve for repairs and moving. Deduct those from what you have saved before entering the number. A buyer who puts down every last dollar to cross the 20% LVR line — the threshold that avoids Lenders Mortgage Insurance — and then settles with an empty emergency fund has traded LMI for financial fragility. First home buyers should also check the Home Guarantee Scheme caps, which allow a 5% deposit without LMI. The calculator's affordable price is only as safe as the reserves left behind after funding it.
- 3
Test the Result Against Your Real Budget, Then Adjust
Take the maximum repayment the calculator produces and add it to a real monthly budget: your actual rent today is gone, but every other line stays, plus maintenance, utilities, and commuting for the new location. Does the remainder still fund your super contribution, your emergency-fund build, and your spending? If yes, the number holds. If the house repayment crowds out any of those, lower the DTI target and re-run until the remainder comfortably covers them. The iterative loop — compute, check against the real budget, adjust — is the discipline that separates a sustainable purchase from an approved-but-unaffordable one. The bank's approval gets you to the auction; this check decides whether you should bid.
Real-World Examples
The Nguyens Bought Below Their Approval and Kept Investing
The Nguyens, earning $165,000, were pre-approved near $780,000. They ran the affordability calculator at a 30% DTI, subtracted their $950 in existing debt repayments, and landed on a comfortable price of about $660,000. They bought a home at that level with their $140,000 deposit and kept salary sacrificing into super at the same pace. Ten years later, their portfolio contributions — the margin the smaller purchase preserved — had grown substantially, and their home had appreciated comfortably. By contrast, two friends who spent their full approval at the same time were still stretched under an oversized mortgage years later. The Nguyens' advantage was not the house; it was the investment plan the comfortable number protected.
Marcus Stress-Tested the Rate and Caught the Buffer
Marcus, a first home buyer earning $95,000, found a home he loved and assumed the quoted repayment was the real one. He ran the calculator and re-ran it at his offered rate plus 2% to mimic the APRA buffer — the true stress-tested repayment was several hundred dollars higher, pushing his DTI past his comfort ceiling. He either negotiated the price down or widened his search; either way, he caught the gap before the hammer fell, not after. The lesson: the repayment on the listing is only as accurate as the rate assumptions behind it, and one stress-test run is the cheapest insurance against buying a monthly surprise.
Elena Kept the Cushion and Rode a Rate Drop
Elena had enough saved for 25% down, but the calculator showed she could preserve a larger emergency fund by putting down 20% and keeping the rest liquid. She chose the 20% route, buying slightly less house than she might have, and her DTI sat comfortably below 30%. Eighteen months later, mortgage rates fell as the RBA cut the cash rate. Because she had retained reserves and her repayment headroom, she refinanced without strain, dropped her rate, and reduced her monthly payment while her retained cash had quietly compounded. Had she stretched to the maximum deposit and maximum price, she would have had neither the cushion to weather the wait nor the flexibility to capitalise on the rate drop when it arrived.
Glossary of Terms
- Debt-to-Income (DTI) Ratio
- Total monthly debt repayments divided by monthly gross income, expressed as a percent. Australian lenders cap DTI for serviceability and APRA asks them to limit DTI above 6× income to a minority of new lending.
- Serviceability Buffer
- The extra interest rate (commonly around 3%) that lenders add to your loan rate when testing your ability to repay, as required by APRA. Your loan is assessed at rate plus buffer, not at the quoted rate.
- Comfortable Price
- A target home price set modestly below the maximum a lender will approve, chosen to preserve cash flow for super, emergency savings, and living expenses rather than spending the full approval amount.
Frequently Asked Questions
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Ivy Sinclair-Wren
Financial Chaos Analyst
Ivy Sinclair-Wren is a Financial Chaos Analyst covering investing, AI, wealth psychology, and the emotional consequences of opening finance apps during market crashes. Based in Melbourne, she specializes in demystifying the Australian tax code and helping users navigate the intersection of spreadsheet logic and human irrationality.