Calculate your New Zealand home loan repayments — fortnightly, monthly, or weekly — across fixed and floating structures. Built for Kiwi borrowers, with full support for the OCR-driven rate environment, break-cost trade-offs, and the new RBNZ DTI rules.
How home loan repayments work in New Zealand
NZ home loan repayments are calculated using the standard amortisation formula, the same maths used worldwide:
Repayment = P × r × (1 + r)^n / ((1 + r)^n − 1)
Where P is the loan principal, r is the interest rate per repayment period, and n is the number of repayment periods.
What makes the NZ market distinctive isn't the maths — it's the fixed-rate culture. Around 80–85% of New Zealand mortgages are fixed at any given time, typically for 1 to 5 years. The most popular terms are 1-year and 2-year fixes, and most borrowers re-fix at the end of the period rather than refinance to a new bank.
Standard loan term is 30 years for owner-occupiers. Most banks offer terms from 1 to 30 years, but anything beyond 30 is unusual and anything less than 20 is typical only for re-fixers wanting to clear the balance faster.
Fixed vs floating: when each makes sense
A fixed-rate loan locks the interest rate for a set term (commonly 6 months, 12 months, 18 months, 2 years, 3 years, 4 years, or 5 years in NZ). For that term, your repayment is predictable. Banks fund fixed lending in the wholesale swap market, where they typically borrow more cheaply than overnight cash — so fixed rates are usually 1.0–1.5% lower than floating in normal conditions.
A floating rate moves with the OCR (and the bank's own funding cost decisions). It's typically the highest rate the bank offers, but it comes with flexibility: you can make unlimited extra repayments without break costs, and you can repay the whole loan at any time without penalty.
The most common NZ structure is a split:
- 70–80% fixed (often as multiple smaller fixes ladder-rolling at different dates) — for repayment stability
- 20–30% floating — for extra-repayment flexibility, redraw, or a revolving credit facility
Splitting smooths re-fix risk: if rates have moved sharply by the time one tranche rolls, only part of your loan is exposed.
The OCR and how it affects your mortgage
The Official Cash Rate (OCR) is set by the Reserve Bank of New Zealand and is the rate banks earn on overnight reserves. Changes to the OCR feed directly into floating mortgage rates — usually within one to two weeks of an OCR announcement.
Fixed mortgage rates don't move with the OCR directly. They're priced off the wholesale swap market, which prices in expectations of where the OCR will be over the fixed term. This is why fixed rates can move before an OCR decision: markets price in the expected change, banks adjust fixed offers, and the OCR change itself only confirms what's already happened.
A practical implication: if you fix when markets expect rates to fall, the fixed rate already includes that expected fall. The benefit of being right about future falls is captured by floating, not by fixing now and re-fixing lower later.
Break costs explained
If you repay or refix a fixed-rate loan before the fixed term ends, your bank may charge break costs (also called Early Repayment Recovery Costs, or ERRC). The mechanism:
- When the bank wrote your fixed loan, it raised matching wholesale funding at the swap rate at that time
- If wholesale rates have fallen since then, the bank's funding contract is now worth more than your loan rate covers
- Releasing you early means the bank takes a loss on the funding it can't redeploy at the original yield
- The break cost recovers that loss — roughly, the present value of the rate differential over the remaining fixed term
Break costs can be tens of thousands of dollars on a large loan when rates have fallen meaningfully. They can also be zero or near-zero when rates have risen since you fixed (the bank is happy to release you because they can re-lend the funds at a higher rate).
Always request a written break-cost figure from your bank before refixing, refinancing, or making a large lump-sum repayment. The figure is valid for a short window (usually 1–7 days) because it moves with the swap market.
KiwiSaver first-home withdrawal
If you've been a KiwiSaver member for at least 3 years and you meet the first-home buyer criteria, you can withdraw most of your KiwiSaver balance — leaving a minimum $1,000 in the account — to put toward your deposit on a first home.
Effect on your loan:
- Smaller loan principal, smaller monthly repayment, less total interest
- Higher LVR position (more deposit means lower LVR), which can mean better rates and avoiding low-equity premiums
- Faster pre-approval, since deposit composition is one of the slowest verification items
A $40,000 KiwiSaver withdrawal on a 30-year loan at 6% is worth around $216/month in repayment savings, or roughly $77,000 in lifetime interest. Stack it with the First Home Grant (administered by Kāinga Ora, $3,000–$10,000 for eligible buyers) to compound the deposit benefit.
Use the KiwiSaver Calculator to project your balance and the maximum first-home withdrawal you could make.
RBNZ DTI rules and how they affect borrowing
From 1 July 2024, RBNZ requires banks to apply Debt-to-Income (DTI) limits on new mortgage lending:
- Owner-occupiers — maximum DTI of 6× household gross income
- Investors — maximum DTI of 7× household gross income
Banks have speed limits (a small portion — currently around 20% — of new mortgage lending can exceed the DTI cap), so the rules don't make above-cap loans impossible, just rationed.
Worked example: a couple earning $200,000 combined gross faces a $1.2m owner-occupier DTI cap. If they need $1.4m to buy in central Auckland, they're either pushed into the speed-limit allocation (subject to bank discretion) or required to bring more deposit so the loan size drops below $1.2m.
DTI rules sit alongside the existing LVR rules:
- 80% LVR cap for owner-occupiers (banks can write up to 20% of new lending above this)
- 65% LVR cap for investors (banks can write up to 5% above)
Both caps apply simultaneously — the binding one is whichever is tighter for your specific situation. For a full broker-side view of the DTI impact, see the RBNZ DTI rules guide.
Refinancing in NZ: when it pays off
Refinancing — switching your mortgage to another bank — is unusually attractive in New Zealand because of the cashback culture. Major banks routinely offer cashbacks of $3,000–$5,000 (sometimes higher for large loans) to switching customers, plus rate specials below the carded rate.
Net economics of a switch:
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- Cashback
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- Rate saving over the new fixed term
- − Break costs on the existing fixed loan (if mid-term)
- − Legal fees (typically $1,000–$2,000)
- − Discharge fees (small — usually $150–$500)
The cleanest refinance window is at re-fix: your existing fixed term is rolling off, break costs are zero, and you can choose any bank without penalty. This is the time most NZ borrowers shop offers.
Mid-fix refinancing is occasionally still profitable when rates have risen since you fixed (so break costs are zero or negative) and the cashback is generous. It's almost never profitable when rates have fallen meaningfully since you fixed (break costs eat the cashback and more).
Run your specific scenario in the calculator above with both your current rate and the offered new rate to see the monthly saving over the new fixed term.
Frequently asked questions
How accurate is this NZ mortgage calculator?
The maths is exact — it follows the standard amortisation formula every NZ bank uses. Variance comes from the inputs: your bank's posted rate vs the rate you're actually offered (specials and broker-negotiated rates often beat the carded rate by 0.10–0.30%), and the difference between assumed-rate scheduling and actual day-count interest accrual. Use this for planning; verify with your bank's quote before signing.
Should I fix or float my NZ home loan?
Most New Zealand borrowers fix — typically 1 or 2 years. Fixing locks in your rate for stability and is cheaper than floating in normal conditions because banks fund their fixed lending in the wholesale swaps market more cheaply than overnight cash. Floating is more flexible (no break costs, unlimited extra repayments) but typically 1.0–1.5% more expensive. The most common compromise is a split: 70–80% fixed, 20–30% floating, so you can make extra repayments on the floating portion without break costs.
How does the OCR affect my home loan?
The Reserve Bank of New Zealand's Official Cash Rate (OCR) is the rate banks pay to borrow short-term funds. Floating mortgage rates move closely with the OCR — usually within a week or two of an OCR change. Fixed rates are driven by the wholesale swaps market, which prices in expectations of where the OCR will be over the fixed term. So fixed rates can move ahead of the OCR if markets expect a future move; they don't always step in lockstep with the official rate.
What are break costs and how are they calculated?
Break costs (formally 'early repayment recovery costs' or ERRC) are charges the bank levies if you repay or refix a fixed-rate loan before the fixed term ends. The calculation: the bank funded your fixed loan by raising matching wholesale funding; if wholesale rates have fallen since then, the bank loses money releasing you early. The break cost is roughly the present value of that loss. Break costs can be tens of thousands on a large loan when rates have fallen — and zero (or near-zero) when rates have risen. Always ask your bank for a written break-cost figure before deciding to refix or refinance.
How does KiwiSaver first-home withdrawal change my loan?
If you've been in KiwiSaver for at least 3 years and meet the first-home buyer criteria, you can withdraw most of your KiwiSaver balance (leaving a minimum $1,000) toward your deposit. This reduces the loan size you need, which directly reduces your repayment and total interest. A $40,000 KiwiSaver withdrawal on a 30-year loan at 6% is worth around $216/month or roughly $77,000 in lifetime interest. The First Home Grant (a separate scheme via Kāinga Ora) can layer on top for eligible buyers.
What are the RBNZ DTI rules and how do they affect borrowing?
From 1 July 2024, RBNZ requires banks to apply Debt-to-Income limits on new mortgage lending: a maximum DTI of 6× for owner-occupiers and 7× for investors. Banks have 'speed limits' — they can write a small portion (around 20%) of new lending above the cap. The DTI is calculated as total household debt divided by gross household income. For a couple earning $200,000, that's a $1.2m maximum loan as an owner-occupier. The DTI rules sit alongside the existing LVR rules (typically 80% LVR cap for owner-occupiers, 65% for investors).
Is refinancing to another bank worth it in NZ?
Often yes. NZ banks routinely offer cashback incentives ($3,000–$5,000) to attract switching customers, plus rate specials. Net of break costs and a small legal fee, refinancing can be cashflow-positive in the first year. The maths shifts depending on where you are in your fixed term — refinancing during a fixed period almost always triggers break costs. The cleanest time to switch is at re-fix, when your fixed rate is rolling off anyway.
Can I make extra repayments on a fixed-rate NZ loan?
Most NZ banks allow some extra repayment on fixed loans — typically up to 5% of the loan balance per year without triggering break costs. Above that, break costs may apply. The standard workaround is a fixed/floating split: keep most of the loan fixed for stability, run a smaller floating portion (e.g. $50,000) where you can make unlimited extra repayments and offset behaviour without restriction. Confirm your bank's specific extra-repayment allowance — they vary.
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Last updated: 27 April 2026