In short: This calculator shows your repayment at your current rate and after rises of 0.25, 0.50, 1, 2 and 3 percentage points. On a $600,000 loan over 30 years at 6.00% p.a., each 0.25 point rise adds about $97 a month, a 1 point rise about $395, and a 3 point rise about $1,231. If the 3 point figure pushes repayments past 30% of gross household income, build a buffer now.
- Current repayment$3,728.67 / month
- +0.25% (6.35%)$3,824 / month (+$96)
- +0.50% (6.60%)$3,921 / month (+$192)
- +1.00% (7.10%)$4,117 / month (+$389)
- +2.00% (8.10%)$4,522 / month (+$793)
- +3.00% (9.10%)$4,940 / month (+$1,212)
- Share of take-home pay at +3%52% — high stress
Lenders assess you at your rate plus 3 percentage points. Over 30% of take-home pay on repayments is commonly called mortgage stress.
Repayment if rates rise 3% (APRA buffer): $4,940 / mo
That is a general estimate on standard assumptions. Every lender applies its own expense benchmarks, income shading and policy, so the real figure moves from lender to lender. Gorakh spent years as a senior credit officer deciding exactly these questions. Send him the numbers above and he will tell you what is realistic and which lenders fit — at no cost to you for home loans.
- A former senior credit officer reads itGorakh assessed loan applications on the lender side before he became a broker.
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The point of a stress test is not to predict the RBA. It is to know, in dollars, how much room your budget has before a rise becomes a problem.
How this calculator works
Enter your loan balance, current rate, remaining term and repayment type. The tool recalculates the repayment at each higher rate with the remaining term held fixed, shows the annual cost of each rise and, if you enter gross household income, the share of income each repayment consumes.
What counts as mortgage stress
The common rule of thumb is that a household is in mortgage stress when repayments exceed 30% of gross income. It is a blunt measure: a family on $250,000 can comfortably spend 35%, while a family on $90,000 with three children may struggle at 25%. Treat 30% as a warning line, not a verdict.
Repayments after a rate rise
The table below assumes a 30-year principal-and-interest loan at 6.00% p.a. for illustration. Your own rate will differ, but the dollar gap between columns is what matters.
| Loan amount | At 6.00% | +0.25% | +0.50% | +1.00% | +2.00% | +3.00% |
|---|---|---|---|---|---|---|
| $400,000 | $2,398 | $2,463 | $2,528 | $2,661 | $2,935 | $3,218 |
| $500,000 | $2,998 | $3,079 | $3,160 | $3,327 | $3,669 | $4,023 |
| $600,000 | $3,597 | $3,694 | $3,792 | $3,992 | $4,403 | $4,828 |
| $750,000 | $4,497 | $4,618 | $4,741 | $4,990 | $5,503 | $6,035 |
| $1,000,000 | $5,996 | $6,157 | $6,321 | $6,653 | $7,338 | $8,046 |
A single 0.25 point move is small on its own. But rises rarely come alone: four of them turn into $395 a month extra on a $600,000 loan, and a full 3 point cycle adds $1,231 a month, almost $14,800 a year.
Why lenders test you at +3%
APRA requires lenders to assess every new home loan at the actual rate plus 3 percentage points. Offered 6.00%, you are checked at 9.00%. That is why your borrowing power is lower than a simple repayment-to-income sum suggests, and why a rise of up to 3 points should, in theory, be survivable for anyone approved under the rule.
The buffer assumes your income, expenses and other debts stay as they were at application. New children, a car loan or a second property erode the cushion, so run this test once a year.
Worked example
A Craigieburn couple owe $600,000 at 6.00% p.a. with 30 years remaining on a combined gross income of $160,000 ($13,333 a month).
| Scenario | Monthly repayment | Share of gross income | Extra per year |
|---|---|---|---|
| Current rate 6.00% | $3,597 | 27% | |
| Two rises, 6.50% | $3,792 | 28% | $2,340 |
| Four rises, 7.00% | $3,992 | 30% | $4,740 |
| Full cycle, 9.00% | $4,828 | 36% | $14,772 |
At 7.00% they touch the 30% line; at 9.00% they are well past it. The sensible move is to treat the $1,231 gap as their target buffer and start building it now.
What to do with the result
Build an offset buffer
Money in an offset account cuts interest today and sits ready to cover higher repayments tomorrow. Aim for at least three months of repayments at the +3% figure, about $14,500 in the example above. Paying extra into the loan with redraw works too; the extra repayments calculator shows the interest saved.
Refinance before the pressure hits
If your rate is above what new customers pay, a refinance can absorb one or two rises before they reach your budget. It is assessed with the same 3% buffer, so it is easier while your position is strong. Check the saving with the refinance calculator.
Fix or split part of the loan
Fixing gives certainty on the fixed portion, at the cost of flexibility and possible break fees. A common compromise is a split: fix half, keep half variable with an offset. The split loan calculator models the blend, and our guide on fixed versus variable rates explains when each suits. If a rise would tip you into real difficulty, read your financial hardship rights before you need them.
Frequently asked questions
How much does a 0.25% rate rise add to my mortgage?
On a 30-year principal-and-interest loan at around 6.00% p.a., each 0.25 percentage point rise adds roughly $16 a month per $100,000 borrowed. That is about $65 on a $400,000 loan, $97 on $600,000 and $161 on $1,000,000. The effect is slightly larger on bigger balances and slightly smaller on loans with fewer years remaining.
What is the APRA 3% serviceability buffer?
APRA requires Australian lenders to assess home loan applications at the loan's interest rate plus at least 3 percentage points. If your rate is 6.00%, the lender confirms you could afford repayments at 9.00% before approving you. The buffer applies to new purchases and refinances alike, which is one reason refinancing can be harder after several rate rises.
Is 30% of income on a mortgage too much?
It is the common threshold for mortgage stress, but context matters. Higher-income households can go beyond 30% with room to spare, while households with childcare and school costs may feel squeezed below it. Use 30% as a trigger to review your budget, build an offset buffer and check whether refinancing or a split loan would help.
What should I do if I can no longer afford my repayments?
Contact your lender before you miss a payment. Every lender has a hardship team and must consider a repayment pause, a temporary interest-only period or a longer term. Speak to a broker at the same time about refinancing or restructuring. If the lender will not help, AFCA is free to use. Our guide on mortgage stress covers the steps in order.
Talk to GNT Finance
Gorakh Timilsina spent years as a credit officer assessing whether borrowers could handle higher rates, and now helps Melbourne families structure loans that can take a few rises without drama. Our home-loan service is at no cost to you in most cases. Book a free consultation or call 0426 403 703.
Written by Gorakh Timilsina
Founder, CEO & Senior Mortgage Consultant at GNT Finance. Gorakh started as a broker assistant, spent years as a senior credit officer assessing loan applications, and now helps Melbourne families get the right loan approved. English, Nepali and Hindi spoken.