How the numbers work
Your deposit is your savings plus what you can take out of KiwiSaver: everything except $1,000 in each account, once you've been a member for 3 years. The First Home Grant used to add to it; it closed on 22 May 2024.
The deposit rule sets the most you can pay for a deposit you have. Banks want 20% of the price as standard. Since December 2025 the Reserve Bank has let them make up to 25% of their new owner-occupier loans to people with less, and many lend to first-home buyers with 10%, so the calculator shows 10% as the usual low-deposit route. Kāinga Ora's First Home Loan goes to 5% for buyers under its income caps: $95,000 before tax for one buyer with no dependants, $150,000 for everyone else. It carries a 1.2% insurance premium on the loan.
The income rule caps the mortgage. Banks may make only 20% of their new owner-occupier loans to people who would owe more than 6 times their income before tax, counting every debt, so the calculator takes 6 times your income, less your other debts, as the most you can borrow. A First Home Loan is exempt from the rule, but its lender still checks you can afford it, so the same figure is used there as a guide. When it is lower than your deposit allows, your income is the limit.
The weekly repayment uses the average one-year fixed rate new borrowers actually paid in the latest month, from What Kiwis Pay, over 30 years. With less than a 20% deposit most banks charge more: a margin of about 0.25% to 1.75% a year, depending on the deposit, or their standard rate.
What it leaves out is the bank's own test: it checks your spending and whether you could keep paying at a higher rate, and some banks will lend less than the rules allow. That part is what a mortgage adviser who works with first-home buyers does, usually at no cost to you, since the lender pays them.
This is a rough guide from public rules, not a loan offer or financial advice. Rules last checked 9 October 2026.