Bank Test Rate Calculator NZ 2026/27
This calculator shows why the loan amount a bank actually approves can be smaller than the loan your advertised mortgage rate seems to support. Banks are required to check that you could keep meeting repayments even if interest rates increased over the life of your loan, so instead of assessing your application at the rate you would genuinely be charged, they run the numbers at a higher internal test rate, sometimes called a servicing rate or assessment rate. Enter the monthly repayment you can comfortably afford, your loan term, the advertised rate you have been quoted, and the bank test rate you want to check against, which defaults to 8.5% but can be changed to match your own bank's figure. The calculator works out the loan amount that repayment would support at each rate, and shows the dollar and percentage gap between them. It updates instantly as you type, with no need to press a button. This is useful for anyone trying to understand why a pre-approval came back lower than expected, for buyers wanting to sanity-check their borrowing power before approaching a bank, and for anyone comparing lenders whose test rates differ. The gap is usually substantial, often 20% or more of the loan amount, which is worth knowing before you set your heart on a purchase price. Figures are indicative estimates on a standard table loan basis, not a lending decision, so confirm your actual servicing position with your bank or a mortgage adviser.
Advertised rate: not a fixed policy figure. Carded mortgage rates move by bank, term and daily market conditions, so the field defaults to an illustrative 6.00% and should be replaced with the rate you have actually been quoted.
Basis: a standard table (principal and interest) loan, with the loan amount derived from your repayment using the standard annuity formula over the number of monthly payments in your chosen term.
Legal basis for testing: banks' responsible lending obligations under the Credit Contracts and Consumer Finance Act 1986 (as amended) require lenders to assess whether a borrower can meet repayments without substantial hardship; each bank sets its own internal test rate and buffer to do this, and figures are not published as a single mandated number.
Last verified: July 2026, against current published NZ mortgage rate ranges and bank responsible-lending disclosures.
Source data: Reserve Bank of New Zealand and Commerce Commission, lender responsible lending obligations.
What Is a Bank Test Rate (Servicing Rate)?
A bank test rate, sometimes called a servicing rate or assessment rate, is the interest rate a lender uses internally when it checks whether you can afford a mortgage, rather than the actual rate it will charge you. Instead of running your repayment calculation at the advertised rate on your loan documents, the bank recalculates your repayments at a higher rate, then checks whether your income and expenses still leave enough room to cover that higher figure. New Zealand banks currently apply test rates in a range of roughly 8.0% to 9.0%, well above the advertised rates most borrowers are actually quoted, which sit several points lower.
Why Banks Test at a Higher Rate
Home loans in New Zealand typically run for 25 to 30 years, and interest rates over that time will almost certainly move, often more than once. Banks carry a responsible lending obligation under the Credit Contracts and Consumer Finance Act to satisfy themselves that a loan will not cause substantial hardship, which includes the realistic possibility that rates rise after settlement. Testing your serviceability at a buffer rate well above today's advertised rate is how a bank builds a margin of safety into its lending decision, so that approving your loan now does not set you up to struggle at your next fixed-term rollover.
How This Calculator Works
You enter the monthly repayment you can genuinely afford, your loan term, the advertised rate you have been quoted, and the bank's test rate. The calculator applies the standard loan annuity formula in reverse: instead of working out a repayment from a loan amount, it works out the maximum loan amount that repayment would support, at each of the two rates, over your chosen term. The advertised-rate figure shows what your repayment budget looks like on paper. The test-rate figure shows the smaller loan a bank will actually be willing to approve on the same repayment budget, because that is the number its serviceability check is really measuring against.
Bank Test Rate vs Mortgage Stress Test
These two ideas are related but not identical, and it is easy to mix them up. A test rate is applied at the application stage, to work out the maximum loan a bank will approve for a given income and repayment budget. A mortgage stress test takes the opposite starting point: you already have a loan amount in mind, or an existing mortgage, and you want to see how much your repayments would rise if rates increased to a chosen level. If you want to check an existing or planned loan amount against a higher rate, use our dedicated Mortgage Stress Test Calculator. This calculator instead starts from your repayment budget and shows how much smaller your maximum loan becomes once a bank applies its test rate.
What Affects the Size of the Buffer
The gap between the advertised-rate loan and the test-rate loan widens as the difference between the two rates grows, and as the loan term lengthens, because a longer term amplifies the effect of a rate difference on the annuity calculation. It also varies by lender: each bank sets its own test rate and internal serviceability policy, and some also apply additional buffers for expenses, dependants, or existing debt commitments that are not modelled here. That is why two banks can look at the same borrower and arrive at noticeably different maximum loan amounts, even when both are working from the same advertised rate.
Worked Example
Consider a borrower who can comfortably afford a $3,000 monthly mortgage repayment, wants a 30-year term, and has been quoted an advertised rate of 6.00%. At that rate, a $3,000 repayment supports a loan of roughly $500,375. If the bank tests the same repayment at an 8.5% servicing rate, the maximum loan it will approve drops to around $390,161. The difference is about $110,214, or 22% less borrowing power, even though the borrower's actual monthly budget has not changed at all. This is the gap that catches many borrowers by surprise when a pre-approval comes back lower than the figure they mentally budgeted from the advertised rate.
Who This Calculator Is For
This calculator is for anyone trying to understand why a bank's pre-approval or lending decision came back lower than expected, first home buyers and movers wanting to sanity-check their borrowing power before house-hunting, and anyone comparing two or more lenders whose test rates and serviceability policies differ. It is a quick way to see the shape of the gap before you sit down with a bank or broker, rather than a substitute for an actual serviceability assessment, which also weighs your income, expenses, dependants and existing debt in detail.
What This Calculator Assumes
- A standard table (principal and interest) loan, with the loan amount derived from your repayment using the standard annuity formula.
- A bank test/servicing rate in the commonly observed 8.0% to 9.0% range; the 8.5% default is illustrative and editable to match a specific bank's disclosed figure.
- The advertised rate is whatever you enter; it is not a fixed policy figure, since carded mortgage rates change by bank, term and market conditions.
- No allowance for other bank-specific serviceability buffers, such as expense haircuts, dependant allowances, or existing debt commitments, which a full application will also assess.
- Results are indicative only and are not a lending decision. Confirm your actual borrowing power with your bank or a mortgage adviser.
Related Mortgage Calculators
- Mortgage Stress Test Calculator: check how much repayments on a known loan amount would rise at a higher rate.
- DTI Income Multiple Calculator: the other major limit on borrowing, the RBNZ 6x/7x income multiple cap.
- Borrowing Capacity Calculator: a fuller estimate of how much a bank might lend you based on income and expenses.
- Loan-to-Value Ratio Calculator: work out your LVR and deposit requirement, the third key lending limit.
- Mortgage Refinance Calculator: check whether switching lenders or rates is worth it.
- Open Banking Explained: background on this topic.
Official NZ sources
This calculator is built from primary New Zealand sources. Always confirm current figures against the official source for your situation:
- Commerce Commission: lender responsible lending obligations under the CCCFA
- Reserve Bank of New Zealand: monetary policy and interest rate context
- Reserve Bank of New Zealand: understanding debt-to-income restrictions (the related RBNZ lending limit)
Frequently asked questions
What is a bank test rate or servicing rate?
A bank test rate, also called a servicing rate or assessment rate, is the higher interest rate a bank uses internally to check whether you could still afford your mortgage repayments if interest rates rose, rather than the actual rate you would be charged today. New Zealand banks currently set test rates in a range of roughly 8.0% to 9.0%, well above typical advertised rates.
Why don't banks assess me at the rate I'm actually being offered?
Under their responsible lending obligations, banks must be reasonably satisfied you could keep meeting repayments even if rates increase over the 25 to 30 year life of a loan. Testing serviceability at a rate several points above the advertised rate builds in a buffer against future rises, so approving a loan today does not set a borrower up to struggle at the next refix.
How much smaller is my approved loan under the test rate than the advertised rate?
It depends on the gap between the two rates and the loan term, but the reduction is often 20% to 25%. For example, a repayment that supports roughly $500,000 at an advertised 6.00% rate over 30 years supports only around $390,000 once tested at 8.5%, a reduction of about $110,000, or 22%.
Is a bank test rate the same as a mortgage stress test?
They are closely related but answer different questions. A test rate is used when a bank assesses a new application, to work out the maximum loan it will approve. A mortgage stress test checks an existing or proposed loan amount to see how much repayments would rise if rates increased, which is useful once you already know the loan size.
Do all New Zealand banks use the same test rate?
No. Each bank sets its own test rate as part of its internal responsible lending policy under the Credit Contracts and Consumer Finance Act, and the figure is not published as a single fixed number. Test rates commonly sit in an observed 8.0% to 9.0% range and can move when a bank reviews its lending settings, so confirm the current figure with your bank or a mortgage adviser.
Can I do anything to reduce the impact of a bank's test rate?
You cannot negotiate the test rate itself, but you can improve the loan size it supports: reduce other debt, extend the loan term, increase your deposit so you need to borrow less, or add income the bank will count toward serviceability. A mortgage adviser can also point you toward a lender whose current servicing policy suits your situation better.
Does the test rate change automatically when advertised mortgage rates change?
Not automatically, and not always by the same amount. Banks review their test rates periodically based on their own view of interest rate risk, so the buffer between the advertised rate and the test rate can widen or narrow independently of movements in carded rates.
Why would a bank decline me even though I can clearly afford the actual repayment?
Because approval is based on the test-rate repayment, not the repayment you would actually pay today. If your income and expenses comfortably cover the advertised-rate repayment but not the higher test-rate repayment on the same loan, the bank will decline or reduce the loan even though your real, current repayment is affordable.
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