Mortgage stress-test calculator — the rate banks actually approve you at
Enter your loan, current rate and term. We'll show your repayment today vs at the bank's stress-test rate — and whether the stressed repayment fits inside a sensible share of your gross income.
The rate that decides your approval, not the rate you'll actually pay.
Banks don't approve you against today's actual interest rate. They approve you against a higher "stress rate" so that if rates rise, you still won't default. This calculator shows you both numbers side by side, plus the share of your gross income each one consumes.
New Zealand
Most NZ banks currently servicing-test at around 8.5%, regardless of your actual fixed rate. The number moves with the OCR but rarely advertises itself — ask your broker for the current servicing rate of each bank you're shortlisting.
Australia
APRA requires a serviceability buffer of at least 3% above the actual rate (raised from 2.5% in 2021). So a 6.4% offer is tested at 9.4%. The buffer applies to the loan you're applying for and any existing debts.
United States
Conventional fixed-rate loans use the actual rate (the rate is locked for the loan's life so there's no rise-risk to stress-test). ARM loans use the higher of the fully-indexed rate or the rate at year 5 — that's the "qualifying rate".
The 30% threshold
A long-standing rule of thumb is that your housing repayment shouldn't exceed 30% of your gross income. Above that, lenders flag you as in "mortgage stress" — but it's a heuristic, not a hard cap. Override the threshold field to model your own bank's policy.
Stress-test calculator FAQ
What is a mortgage stress test?
It's the higher rate banks use to test whether you can afford a loan, even if interest rates rise. They don't approve you against today's actual rate — they approve you against a stressed version, so a future rate rise doesn't push you into default. The 'stress rate' is the input the bank cares about most for serviceability.
What stress rate do NZ banks use?
Most NZ banks test serviceability at around 8.5% as of 2025-26, regardless of your actual fixed rate. The exact number changes when the OCR shifts; banks publish their current servicing rate but rarely advertise it. We default to 8.5% because that's the most common across the big four.
And in Australia?
APRA requires a buffer of at least 3% above the actual rate (it was 2.5% before 2021). So if your offer is 6.4%, the bank tests at 9.4%. We default to actual + 3% but you can override it.
How is the US different?
US conventional mortgages use the actual loan rate for qualification (the rate is fixed for the life of the loan, so there is no rate-rise risk to stress-test). For ARM loans, lenders use the "qualifying rate" — typically the higher of the fully-indexed rate or the rate at year 5. We default the stress rate to equal the actual rate for US fixed loans; bump it for ARM modelling.
Run the rest of the numbers
DTI calculator
See whether your next loan fits inside the RBNZ / APRA / US DTI cap before you talk to a bank.
LVR calculator
Work out your LVR (or LTV in the US) and the deposit you need to clear investor and owner-occupied bands.
Cashflow calculator
Weekly and annual net cashflow on a rental, with rates, insurance, management, vacancy and interest baked in.
Rental yield calculator
Gross yield, net yield and cap rate for any rental — with weekly-rent input for NZ/AU and monthly for the US.
Stress-test the loan, then stress-test the portfolio.
Stackhold runs the same calculation across every property and shows you which ones break first.
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