Property Purchase Scenario Model Calculator NZ
The Property Purchase Scenario Model Calculator is a complete home-buying planner for New Zealand. Rather than giving you a single vague borrowing figure, it recreates the way a bank actually decides how much you can spend, then goes further and tells you the one thing standing between you and a bigger budget. Enter your before-tax income, any properties you own, your cash, your KiwiSaver and your debts, and the model turns all of that into a realistic purchase price, a deposit breakdown, an estimated repayment, and a plain-English diagnosis of what is limiting you.
It is built for the real decisions people face. A first home buyer can see how their KiwiSaver and savings turn into a deposit. Someone trading up can model selling their current home, releasing the equity, and buying the next one. An investor can compare keeping a rental against selling it. You can add up to ten properties, switch each one between sell, keep and live in, or keep and rent out, and watch the affordable price change instantly. Every figure and control has a plain-language explanation, and you can adjust the assumptions, such as the test rate and the debt-to-income multiple, to match your own lender.
Your income
Your income before tax (per year)iYour pay before tax is taken out. It is the salary on your employment agreement or a job ad, not what lands in your bank account. Banks use this before-tax figure to work out how much you can borrow.
Partner or co-buyer income before tax (optional)iAdd a partner or co-buyer's before-tax pay if you are buying together. Leave it blank if you are buying on your own.
What you own
Properties you already own. Selling one frees up its equity for your deposit. Keep one and its mortgage still counts against you.iAdd each property you own. Choosing Sell frees up the equity (sale value minus the mortgage) for your deposit. Choosing Keep leaves the mortgage on your books, which reduces how much more you can borrow.
Cash savings you can useiMoney you have saved that you can put towards the purchase, on top of any equity you release by selling.
KiwiSaver balance (combined)iYour and your partner's total KiwiSaver. If this is your first home you can usually withdraw it for the deposit, but you must leave at least $1,000 in the account.
Debts and living costs
Other debt repayments (per month)iMonthly payments on other debts such as a car loan, personal loan or credit card. These reduce how much of your income is left to cover a mortgage.
Other debt balances still owingiThe total you still owe on those other debts. This counts towards the Reserve Bank debt-to-income limit, so it can reduce your borrowing power.
Number of dependantsiChildren or others who depend on you. More dependants means higher living costs, which banks build into their affordability test.
Living costs (per month)iYour estimated monthly spending on everything except the mortgage: food, power, transport, insurance, phone and so on. Banks use a figure like this to check you can still afford to live once the mortgage is added.
Benchmark for your household: $4,800.00 per month.
The purchase
Buying asiOwner-occupier means you will live in the home. Investor means you will rent it out. Investors need a bigger deposit (about 30 percent) but get a slightly higher debt-to-income limit (7 times income).
Assumptions edit to match your lender
Test rateiThe higher interest rate a bank pretends you are paying when it checks you can afford the loan. It is a safety buffer so you can still pay if rates rise. Banks are around 6.85 to 7 percent right now, so 8 percent adds a sensible margin.
Actual rateiThe real interest rate you would actually pay today. It is used only to show your likely repayment, not to test whether you qualify.
Loan termiHow many years you take to pay off the mortgage. 30 years is common. A longer term means lower repayments but more interest paid overall.
DTI, owner-occupieriDebt-to-income limit. The Reserve Bank caps most owner-occupier home loans at 6 times your before-tax income, counting all your debt.
DTI, investoriThe debt-to-income limit for investors is higher, at 7 times before-tax income.
Comfort limitiThe share of your before-tax income going on mortgage repayments above which housing starts to feel tight. 30 to 40 percent is the usual guide, so we flag anything over 35 percent.
Deposit, owneriThe smallest deposit lenders usually accept for an owner-occupier, as a share of the price. Around 20 percent under the loan-to-value rules.
Deposit, investoriThe smallest deposit lenders usually accept for an investor, around 30 percent of the price.
Deposit, new buildiNew builds are exempt from the loan-to-value limits, so a smaller deposit, often around 10 percent, can be enough.
Selling costiWhat it costs to sell a property, mainly the real estate agent's commission plus GST and marketing. Around 4 percent is typical, and it comes off the equity you release.
Buying costsiOne-off costs of buying, such as your lawyer, a LIM report and a builder's report. These come out of your deposit.
The green line marks the price you can afford, the lowest of the three ceilings. The amber bar is the test that limits you.
What the Property Purchase Scenario Model Calculator does
Most online tools answer only half the question. They tell you a borrowing number and stop there. This model answers the whole question. It takes your real financial position, applies the same three tests a New Zealand bank applies, and returns the property price you can realistically buy, the deposit you will have, the repayment you will make, and, most usefully, the single reason you cannot buy more. Understanding that reason is what turns a number into a plan, because the fix is completely different depending on which test is holding you back.
The three tests, and why the lowest one wins
A bank will only lend to the point where all three of its tests pass, so your true limit is the lowest of them. The first is serviceability. The bank takes your after-tax income, adds 80 percent of any rent from a property you keep, then subtracts your living costs and other debt payments. Whatever is left has to cover the new mortgage repayment, and the bank checks this not at today's interest rate but at a higher test rate, so you could still cope if rates rose. The second test is the Reserve Bank debt-to-income cap, which since July 2024 limits total debt to about 6 times a household's before-tax income for owner-occupiers and 7 times for investors. The third is the deposit, set by loan-to-value rules at roughly 20 percent for owner-occupiers and 30 percent for investors. New builds are exempt from the second and third tests, which is why the new build switch can lift your budget noticeably.
How the inputs and controls change the answer
Every field moves the result in a way that mirrors real life. Raising your before-tax income lifts both the serviceability ceiling and the debt-to-income ceiling. Adding a property to sell increases your deposit through the equity you release, after selling costs and any bright-line tax, while choosing to keep and rent that property instead adds rental income but also keeps its mortgage on your books, which can pull down the debt-to-income ceiling. Your living costs and other debts feed straight into serviceability, so clearing a car loan can free up more than people expect. The assumptions matter too. Lowering the test rate, as happens when the Reserve Bank cuts the official cash rate, lifts serviceability; changing the deposit percentage or the debt-to-income multiple lets you model a specific lender or a first home loan with a low deposit. Because the tool shows all three ceilings side by side, you can see at a glance whether earning more, saving more, or clearing debt is the fastest route to the home you want.
How this helps you
Buying a home is the largest financial decision most New Zealanders ever make, and going into it with a clear, honest number changes how you approach it. If you are saving for a first home, the model shows how close you are and whether your deposit or your income is the barrier, so you can focus your effort where it counts. If you are trading up, it lets you test selling versus keeping before you commit, and see the equity you would really walk away with after costs. If you are an investor, it puts the deposit, the debt-to-income cap and the rent all in one place. And because you can pin one scenario and compare it against another, you can answer the questions that keep buyers up at night, such as whether it is better to sell the rental or keep it, or how much a pay rise would actually add to your budget. It is general information rather than a lending decision, so treat it as a fast, private way to get your bearings before you talk to a mortgage adviser or your bank.
Who this calculator is for
First home buyers working out if they are ready, existing owners planning a move up or down, investors weighing a purchase, and anyone who wants to understand their borrowing power before they start looking. It suits single buyers and couples, and it handles complex situations with multiple properties that simpler tools cannot.
What this calculator assumes
Your before-tax income is converted to after-tax income using the 2026/27 PAYE tax brackets and the 1.75 percent ACC earners' levy. Serviceability is tested at an 8 percent rate by default, above the roughly 6.85 to 7 percent that banks currently use, as a buffer. The debt-to-income cap defaults to 6 times income for owner-occupiers and 7 times for investors, and the deposit to 20 percent for owner-occupiers and 30 percent for investors, with new builds exempt from both. Rent on a kept property is counted at 80 percent. Selling costs default to 4 percent and buying costs to a fixed sum. Regional median prices are REINZ median sale prices from May 2026 and should be refreshed against the latest REINZ data, since medians move every month. All of these can be edited. This is a general information tool and not financial advice or an offer of lending.
Related calculators and guides
Continue with the borrowing capacity calculator, the mortgage repayment calculator, the house deposit savings calculator and the KiwiSaver first home withdrawal calculator. To understand the rules, read the learning centre guides on buying your first home, LVR restrictions, debt-to-income limits and mortgage pre-approval.
Official NZ sources
Debt-to-income and loan-to-value settings are from the Reserve Bank of New Zealand. Mortgage test rates are tracked by interest.co.nz. Affordability guidance is from Sorted. Tax rates are from Inland Revenue.