australia • AUD

Mortgage Stress Test Calculator (Australia)

Test your mortgage affordability if interest rates rise. APRA stress test calculator for Australian home loans. Check repayment impact from rate increases.

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Current loan details

Loan amount

Current interest rate (%)

Loan term (years)

Stress test settings

Stress test interest rate (%)

Repayment type

Financial Disclaimer: This result is an educational estimate produced by applying a standard formula to the figures you entered. It is not an offer, a quotation, or financial advice: real costs and returns depend on a provider's pricing, fees and underwriting, and on circumstances this calculator does not collect. Confirm the figures with the provider or a qualified adviser before acting on them. Full disclaimer.

Sources & methodology

Formula:: Scheduled repayment (principal and interest)
Reference:: Australian Prudential Regulation Authority (APRA)

Calculation type: Exact calculation. Figures are taken from Australian Prudential Regulation Authority (APRA) and Moneysmart (Australian Securities and Investments Commission) — see sources below.

Your entries stay on this device. This calculator runs entirely in your browser — the figures you type are not sent to us or to anyone else. The page itself uses cookies for analytics and advertising, described in the privacy policy.

Formula & methodology

Formula used

Scheduled repayment (principal and interest)

PMT = P × [ i(1+i)^n ] / [ (1+i)^n − 1 ]

The standard amortisation formula. The repayment is calculated on the FULL loan amount — an offset balance never reduces the scheduled repayment, it reduces the interest charged.

Stressed repayment

PMT_stress = PMT(P, i_stress, n)

The same amortisation formula is re-run at the higher stress rate over the same remaining term and the same loan balance.

Repayment increase

increase = PMT_stress − PMT_current

The extra amount you would need to find each month if rates reached the stress rate.

Variable definitions

Symbol	Meaning	Unit
P	Loan amount. property price minus deposit	AUD
i	Monthly interest rate. annual rate ÷ 12	ratio
n	Number of repayments. loan term in years × 12	months
i_stress	Stress rate. the higher rate being tested, entered by you	% p.a.

Step-by-step calculation

1. Enter the loan as it stands
Balance, current rate, remaining term and repayment type.
2. Choose a stress rate
APRA expects lenders to assess serviceability with a buffer above the loan rate — 3 percentage points at the time of writing. Testing your current rate plus that buffer mirrors a lender's approach; check APG 223 for the buffer currently in force.
3. Compare the two repayments
Both figures use the same balance and term, so the difference isolates the effect of the rate alone.

Limitations

This is not a lender serviceability assessment. A lender also applies income shading, a household expenditure benchmark, existing commitments and card limits — none of which are modelled here.
The APRA buffer is a floor applied by lenders at assessment, not a cap on how far rates can actually move. Choosing a stress rate below your current rate plus the prevailing buffer tests less than a lender would.
Interest-only loans are shown at their interest-only repayment. The step up when the interest-only period ends is usually a larger shock than the rate rise itself, because principal must then be repaid over a shorter remaining term.

This page is educational. It applies a standard formula to the figures you enter and shows the arithmetic behind the result. It is an estimate, not an offer, a quotation or financial advice: real costs depend on the provider's pricing, fees and underwriting, and on circumstances this calculator does not collect.

Sources & references

Prudential Practice Guide APG 223 — Residential Mortgage Lending (serviceability buffer) — Australian Prudential Regulation Authority (APRA)
Home loans — repayments, offset accounts and extra repayments — Moneysmart (Australian Securities and Investments Commission)

Help & FAQs

Frequently Asked Questions

Clear answers to common questions to help you use this calculator confidently.

What results does this mortgage stress test calculator show?

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The calculator shows estimated repayments at your current rate and under stressed rates. This helps you understand potential repayment changes.

Does this calculator reflect Australian lending buffer practices?

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It applies indicative buffers similar to those used by Australian lenders — APRA requires a minimum 3-percentage-point buffer when assessing serviceability. Exact buffers may differ between institutions.

Can investors use this mortgage stress test calculator?

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Yes. Property investors can use it to assess how rate changes may affect cash flow.

What happens if I include extra repayments?

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Extra repayments may reduce loan balance faster and lower future repayments. The calculator can show this impact.

Does this calculator include taxes or other household costs?

Tap to view the answer

No. It focuses on mortgage repayment scenarios only. Other household expenses should be considered separately.

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Mortgage Stress Testing – APRA & Affordability Guide

What Is Mortgage Stress Testing?

Stress testing calculates your mortgage repayment at a higher interest rate than your current rate. It simulates 'worst case' scenarios where rates rise (e.g., from 6.5% to 8.5%), helping you confirm whether you can sustainably afford your mortgage if rates increase.

Why Do Australian Lenders Require Stress Testing?

The Australian Prudential Regulation Authority (APRA) mandates that lenders assess mortgage applications at serviceability rates rather than current rates. Lenders typically stress test at current rate + 2-3% to ensure borrowers can repay even if rates rise. This protects borrowers from over-leveraging in low-rate environments.

APRA Serviceability Buffer – How It Works

APRA requires lenders to test at a 3% buffer above the loan's current rate (minimum). A 6.5% loan is tested at minimum 9.5%+ affordability. This buffer ensures borrowers can service loans if rates rise significantly. It's the key reason why many borrowers are approved for 'less than expected' loan amounts.

Interest Rate Cycles in Australia

Australian interest rates fluctuate with RBA policy (Reserve Bank of Australia). Rates have ranged from 0.1% (2020-2021 pandemic lows) to 11%+ (1980s combating inflation). Current cycle shows rates rising from lows. Historical data: RBA adjusts rates 8-12 times per year on average. Stress test using +1%, +2%, and +3% increases to cover various scenarios.

How Rate Rises Impact Monthly Repayments

Each 1% rate rise increases repayments significantly. Example: $600,000 loan over 30 years: 6.5% = $3,790/month. 7.5% = $4,194/month (+$404). 8.5% = $4,600/month (+$810). 9.5% = $5,006/month (+$1,216). A 3% rise increases payments by $1,200+/month (~32% more). This illustrates why affordability planning is critical.

Stress Testing Scenarios – Plan for Multiple Outcomes

Conservative planning tests three scenarios: Baseline: Current/offered rate. Moderate: Current + 2% (reasonable expectation). Aggressive: Current + 3% (historical high). If you can comfortably afford stressed repayments, you have financial safety margin. If stressed repayment >= 30% of income, reconsider loan size.

Building Financial Resilience & Loan Serviceability

To improve stress test resilience: Build emergency savings (6-month buffer). Avoid new debt while debt servicing is high. Make extra repayments in low-rate periods. Consider annual payments increasing with salary. Refinance if rates drop significantly. These strategies provide cushion if income reduces or rates rise unexpectedly.

Formula & methodology

Formula used

Scheduled repayment (principal and interest)

PMT = P × [ i(1+i)^n ] / [ (1+i)^n − 1 ]

The standard amortisation formula. The repayment is calculated on the FULL loan amount — an offset balance never reduces the scheduled repayment, it reduces the interest charged.

Stressed repayment

PMT_stress = PMT(P, i_stress, n)

The same amortisation formula is re-run at the higher stress rate over the same remaining term and the same loan balance.

Repayment increase

increase = PMT_stress − PMT_current

The extra amount you would need to find each month if rates reached the stress rate.

Variable definitions

Symbol	Meaning	Unit
P	Loan amount. property price minus deposit	AUD
i	Monthly interest rate. annual rate ÷ 12	ratio
n	Number of repayments. loan term in years × 12	months
i_stress	Stress rate. the higher rate being tested, entered by you	% p.a.

Step-by-step calculation

1. Enter the loan as it stands
Balance, current rate, remaining term and repayment type.
2. Choose a stress rate
APRA expects lenders to assess serviceability with a buffer above the loan rate — 3 percentage points at the time of writing. Testing your current rate plus that buffer mirrors a lender's approach; check APG 223 for the buffer currently in force.
3. Compare the two repayments
Both figures use the same balance and term, so the difference isolates the effect of the rate alone.

Limitations

This is not a lender serviceability assessment. A lender also applies income shading, a household expenditure benchmark, existing commitments and card limits — none of which are modelled here.
The APRA buffer is a floor applied by lenders at assessment, not a cap on how far rates can actually move. Choosing a stress rate below your current rate plus the prevailing buffer tests less than a lender would.
Interest-only loans are shown at their interest-only repayment. The step up when the interest-only period ends is usually a larger shock than the rate rise itself, because principal must then be repaid over a shorter remaining term.

Calculator inputs

Current loan details

Stress test settings

Your results

Sources & methodology

Formula & methodology

Formula used

Scheduled repayment (principal and interest)

Stressed repayment

Repayment increase

Variable definitions

Step-by-step calculation

Limitations

Sources & references

What results does this mortgage stress test calculator show?

Does this calculator reflect Australian lending buffer practices?

Can investors use this mortgage stress test calculator?

What happens if I include extra repayments?

Does this calculator include taxes or other household costs?

Related calculators

More Australia calculators

Calculator inputs

Current loan details

Stress test settings

Your results

Sources & methodology

How to Use This Calculator

Example Mortgage Stress Test

Understanding Your Results

Key Tips

Mortgage Stress Testing – APRA & Affordability Guide

What Is Mortgage Stress Testing?

Why Do Australian Lenders Require Stress Testing?

APRA Serviceability Buffer – How It Works

Interest Rate Cycles in Australia

How Rate Rises Impact Monthly Repayments

Stress Testing Scenarios – Plan for Multiple Outcomes

Building Financial Resilience & Loan Serviceability

Formula & methodology

Formula used

Scheduled repayment (principal and interest)

Stressed repayment

Repayment increase

Variable definitions

Step-by-step calculation

Limitations

Sources & references

How to Use This Calculator

Example Mortgage Stress Test

Understanding Your Results

Key Tips

Mortgage Stress Testing – APRA & Affordability Guide

What Is Mortgage Stress Testing?

Why Do Australian Lenders Require Stress Testing?

APRA Serviceability Buffer – How It Works

Interest Rate Cycles in Australia

How Rate Rises Impact Monthly Repayments

Stress Testing Scenarios – Plan for Multiple Outcomes

Building Financial Resilience & Loan Serviceability