Can we actually afford this house?

Almost every line in this calculator drifts upward, and your income may not keep pace. Council rates in Auckland rose 7.9% for 2026/2027: about $320 a year on the average residential property, and the council forecasts increases of up to 3.5% a year after that. Insurance premiums, power and groceries have all been rising faster than wages in recent years. The safe way to use this tool is to run your numbers, then run them again with rates and grocery lines 5-10% higher and see if the surplus survives.

Auckland Council adopted a 7.9% average residential increase for 2026/2027, the largest in the super city's history, mostly to fund City Rail Link operating costs, following 5.8% the year before. Beyond this year the council forecasts stabilising at no more than about 3.5% a year. Rates are struck every July, so treat whatever figure you enter here as this year's number, not a fixed cost.

That is the squeeze that catches most new buyers, because your mortgage repayment is only fixed until your next refix while everything else keeps moving. Check the current food price index and CPI from Stats NZ rather than assuming last year's numbers, and stress-test this calculator by lifting groceries, power and insurance together while leaving income flat. If the surplus goes negative in that version, the buffer, not the purchase price, is what needs fixing first.

Most calculators answer a much easier question: what is the repayment on this loan. That number on its own tells you almost nothing about whether you can live in the house. This one asks for the whole picture, so council rates, insurance, power, transport, childcare and day-to-day spending all sit alongside the repayment, and it shows you three things the others leave out: what is genuinely left over each month, how far interest rates could rise before that surplus disappears, and how long your savings would last if your income stopped. It is built around risk and buffer rather than the maximum you could borrow.

It is worth thinking about, because a mortgage is the largest debt most people ever take on and it does not pause if something goes wrong. The three cover different events. Life insurance pays a lump sum to your family if you die, which can clear the mortgage so they keep the house. Trauma or critical illness insurance pays a lump sum when you are diagnosed with a serious condition such as cancer, a heart attack or a stroke, whether or not you can still work. Mortgage protection, sometimes sold as income protection, instead pays a monthly amount that covers your repayments while you are unable to work. Roughly speaking, life cover protects your family from your death, trauma cover buys you time and choices, and mortgage or income protection keeps the repayments going. Premiums rise with age and health, and cover bought through a bank is not always the cheapest, so it pays to compare or talk to an adviser.

Guessing is the fastest way to get this wrong, so use your own bank statements. Download a CSV of a month, ideally three or four, from your online banking and open it in Excel or Google Sheets. Add a new column and label every row with the type of expense: power, groceries, insurance, petrol, and so on, matching the lines in this calculator. Anything that does not fit a line, tag as day-to-day (or add a new cost line here for it). Then filter or sort by that column and total each group, and use those numbers instead of the estimates above. For day-to-day, divide the month's total by 30 to get the per-day figure. One warning: some months are far more expensive than others: birthdays, Christmas, holidays, car repairs, and those months eat into your savings rather than your surplus, so average across several months if you can.

Add up your household take-home pay, then subtract your mortgage repayment and every other cost of running your life: council rates, insurance, power, transport, groceries, childcare and day-to-day spending. What is left is your monthly surplus. If that number is negative, or so small that one unexpected bill wipes it out, the mortgage is not affordable yet.

With a 20% deposit, an $800,000 house means a $640,000 mortgage. Over 30 years at around 5.8% that is roughly $3,750 a month in repayments alone, before rates, insurance and living costs. Most households need somewhere around $9,000 to $10,000 a month in combined take-home pay to carry that comfortably, but the honest answer depends on your own costs, which is what this calculator is for.

On a $640,000 loan over 30 years, a 1% rise adds roughly $400 a month. That is why the three scenarios above sit side by side at your rate, plus 1% and plus 2%, so you can see whether a rate rise at refix time turns a healthy surplus into a shortfall.

Most lenders want 20% of the purchase price for an owner-occupied home. Some will lend with 10% or less under low-deposit exemptions or First Home Loan criteria, usually with a low equity margin added to your rate. Keep money aside for legal fees, a builder's report and moving costs on top of the deposit.

Council rates (the Auckland average is about $4,378 a year), house and contents insurance, body corporate fees if you are buying an apartment or townhouse, higher power bills than a rental, ongoing maintenance, and the legal and inspection fees at purchase. These are the lines that turn an affordable-looking mortgage into a tight month.

A common rule of thumb is three to six months of total outgoings held in accessible savings, kept separate from your deposit. The runway figure above shows how many months your savings would cover your total outgoings if your income stopped, now and after another 6 or 12 months of saving, so you can size the buffer against your real numbers rather than a rule of thumb.

No. In New Zealand your mortgage repayment covers principal and interest only. Council rates, house insurance and contents insurance are billed separately, so they need to be budgeted as their own lines, and this calculator treats them that way.

No. Everything you type stays in this browser tab only and is gone when you close it. Nothing is sent anywhere. If you want to keep your numbers, use the XLSX download.