The Finance Algorithm

Affordability Stress Tester

Test your loan against rate rises, income drops, and life changes

Updated October 2026Built and checked by MaverickHow it's calculatedReport an error

Your numbers

Updates as you type
$
$600k
%
6.8%
30
$
$8k
$
$4k
$
$20k

The button asks our AI to explain these figures in words.

Mortgage stress test

Current repayment

$3,912

monthly mortgage

Current surplus

$588

after mortgage + expenses

Repayment share

48.9%

of after-tax income

Emergency buffer

2.7 months

target: 3 months

What your budget looks like under each scenario

A negative surplus means the repayment and expenses aren't covered in that scenario. Red bars are the ones to plan around.

$588Current$181Rate +1%-$242Rate +2%-$677Rate +3%-$1,012Income -20%-$2,612Income -40%

Monthly repayment at higher rates

Banks stress-test at your rate + 3%. You should too: that's the +3% bar to plan around.

$3,912Current$4,319+1%$4,742+2%$5,177+3%
Resilience plan
Your emergency fund covers 2.7 months of expenses and repayments; Moneysmart suggests saving about 3 months. At least one income drop leaves a shortfall, so check the loan on one income before committing.

How it works

What happens to your budget if rates rise 1%, 2% or 3%, or if your household income falls by a fifth or two-fifths - after a job change or during parental leave? This stress tester runs each scenario against your loan, income and expenses, and shows how many months your emergency savings would cover.

  1. 1Enter your loan and income details
  2. 2See stress test scenarios automatically
  3. 3Understand your buffer and limits
  4. 4Check your emergency savings against Moneysmart's suggested three months

The figures today

As of 7 November 2026, the lowest variable home loan rate is 5.93%, from SCCU's BROKER HOME LOAN, while the typical best across 104 institutions is 6.38%. The lowest 3-year fixed home loan rate is 6.24%, from Credit Union SA's 3-Year Fixed 40 Year Home Loan Package, while the typical best across 80 institutions is 6.69%. The RBA cash rate is 4.85%. Those are for an owner-occupier paying principal and interest at an 80% LVR.

Home loan rates todayWho passed on the last RBA move

Worked examples

Rate Rise Scenario

The Chens have $7,500 monthly income after tax, $3,200 of expenses and a $520,000 loan at 6.2%. They want to know if they could handle rates 2% higher.

Loan amount
$520,000
Interest rate
6.2%
Loan term (years)
28
Household income (monthly after tax)
$7,500
Monthly expenses (excluding mortgage)
$3,200
Emergency savings
$25,000

Their repayment is $3,265 a month, leaving $1,035 after expenses. At 8.2% it would be $3,955 and the surplus falls to $345. At 9.2% - the 3% buffer lenders test at - they'd be $18 a month short. Their $25,000 covers about 3.9 months of expenses and repayments.

Income Drop Scenario

Maria takes home $9,000 a month, spends $2,800 and has a $480,000 loan at 6.5%. She wants to know if she could manage on $6,500 during parental leave.

Loan amount
$480,000
Interest rate
6.5%
Loan term (years)
30
Household income (monthly after tax)
$9,000
Monthly expenses (excluding mortgage)
$2,800
Emergency savings
$40,000

Her repayment is $3,034, leaving $3,166 a month. On $6,500 she would still have $666 left, so she wouldn't need to draw on savings. Even the calculator's 40% drop, to $5,400, leaves a $434 shortfall that her $40,000 could cover for more than seven years.

Questions people ask

What interest rate should I stress test at?
Lenders test at your rate plus 3 percentage points, the buffer APRA expects. That isn't far-fetched: the RBA raised the cash rate by 4.25 percentage points between May 2022 and November 2023.
How much emergency fund should I have?
Moneysmart suggests about three months of expenses, and more if you're planning further ahead or expect time off work. This calculator counts your mortgage repayment as part of those expenses.

The terms, in plain English

Mortgage Stress
A common measure counts a household as in housing stress when housing costs take more than 30% of gross income, usually applied to lower-income households. It's a rule of thumb, not a lending limit.
Buffer Rate
The additional interest rate (usually 3%) that lenders add when assessing your ability to repay, ensuring you can handle rate rises.
DTI (Debt-to-Income) Ratio
Your total debts divided by your annual gross income. Since 1 February 2026 APRA has limited each bank's new loans at six times income or more to 20% of its lending.

Official sources

Check Your Borrowing Power

See how much lenders will actually approve.

Full Loan Health Check

How your rate, LVR and features stack up.

RBA Impact Analysis

Understand how RBA rate decisions affect your repayments.