NZ Mortgage Calculator.
See your repayment, total interest, and payoff time. Add extra payments or an offset balance to see exactly how much sooner you'd finish. Stress-test a rate rise in one click.
Enter a loan amount to see the repayment.
Updates as you type — no signup needed.
Pay off years sooner.
Each of these shortens your loan without changing your headline rate. Combine them for compound effect.
Pay extra each period
Even $50/fortnight extra becomes $1,300 a year of principal reduction. Compounded over 30 years, that's tens of thousands in interest saved — and several years off the term.
Half-monthly fortnightly
Set your loan up to take *half your monthly payment* every fortnight (talk to your bank). 26 × half = 13 monthly equivalents per year — the extra month knocks 3–5 years off a 30-year loan.
Offset / revolving credit
Savings or salary parked in an offset account reduce the balance that accrues interest. $30k in offset on a 4.5% loan = $1,350/year interest not charged.
Mortgage questions, answered.
Does paying fortnightly really pay off faster?+
Not by itself — a fortnightly schedule uses the same total dollars per year as monthly, so the payoff time is roughly identical. The well-known "saves 3-5 years" trick only works if your loan is set up to take *half your monthly payment* every fortnight (26 × half = 13 monthly equivalents/year). To model that, leave the frequency on monthly and use the 'Pay off faster' panel to add an extra payment.
How does an offset account reduce interest?+
Your savings or salary held in an offset (or revolving credit) account is subtracted from the interest-bearing mortgage balance. If your loan is $500k and you have $50k in offset, you only pay interest on $450k. Your scheduled repayment stays the same, but more goes to principal, so you finish sooner.
Can I make extra repayments on a fixed-rate loan?+
Most NZ banks allow some lump-sum repayment without break fees, but the basis differs: ANZ and Kiwibank let you pay up to 5% of the current loan balance each year; BNZ uses 5% of the loan amount at the start of the fixed term; ASB doesn't offer a 5% no-fee threshold (it has its own ERA rules); Westpac charges break fees on lump sums regardless. Beyond the allowance, break costs can be significant if rates have dropped since you fixed. Check your loan agreement before making a lump sum.
What's the difference between offset and revolving credit?+
They work similarly — both use savings to offset interest. Offset is a separate savings account linked to your mortgage; revolving credit is a home loan facility you can draw down and repay like an overdraft. Revolving credit gives more flexibility; offset is simpler.
Is mortgage interest deductible?+
For your own home — no. For a residential rental, from FY 2025-26 onwards it's fully deductible. If you're working out a rental property, try our Rental Yield calculator — it factors interest and tax in.
Zelvo handles the tax side.
If this mortgage is on a rental property, Zelvo tracks the income, applies the deductions, and produces IR3-ready figures — in about 10 minutes.
This is a guide only, not tax advice. Tax rules change each year and your situation may involve factors not covered here. Consult a registered NZ tax professional or chartered accountant before filing. Zelvo accepts no liability for errors in tax calculations or filings made using this tool.