Home Mortgage Calculator NZ
This calculator works out what a New Zealand home loan will cost you, in regular repayments and over the full term. Enter your home loan amount, annual interest rate, loan term (10 to 30 years), and how often you repay - weekly, fortnightly or monthly. You can also add the property purchase price and deposit to see your loan-to-value ratio (LVR), and enter an extra repayment amount to see how paying more each period shortens your mortgage. It returns your regular repayment, total interest paid over the full term, total amount repaid, and your LVR, plus a full repayment breakdown and the time and interest you would save with extra repayments. A comparison table also shows your repayment, total interest and total repaid at rates from 4.5% to 8%, so you can see how sensitive your mortgage is to rate changes. Use it to test different loan amounts, terms and rates before you commit, to check whether your deposit meets the standard 80% LVR threshold most lenders require, and to see the value of paying extra off your mortgage when possible. Results update instantly as you change any figure. This tool provides indicative estimates only, based on the standard amortisation formula; it excludes lender fees, break costs, insurance and rate changes during your term, so confirm final figures with your bank or a mortgage adviser.
1. Loan Details
2. Optional: Property Details
Repayment Breakdown
With Extra Repayments
Monthly Payment at Different Interest Rates
| Interest Rate | Monthly Payment | Total Interest | Total Repaid |
|---|
How Home Mortgage Repayments Are Calculated
A home mortgage uses a standard amortisation formula. Each period, interest is charged on the outstanding balance; the rest of your repayment reduces the principal. Over time the interest portion falls and the principal portion rises, until the loan is paid off in full at the end of the term.
The formula for a regular repayment M is:
M = P x [r(1 + r)^n] / [(1 + r)^n - 1]
Where P is the loan principal, r is the interest rate per period (annual rate divided by the number of periods per year), and n is the total number of payment periods.
Worked Example
Defaults used in this calculator: loan of $650,000, interest rate of 6.5% per year, 30-year term, repaying monthly.
- Monthly rate r = 6.5% / 12 = 0.54167% = 0.0054167
- Number of payments n = 30 x 12 = 360
- Monthly payment M = 650,000 x [0.0054167 x (1.0054167)^360] / [(1.0054167)^360 - 1]
- (1.0054167)^360 = approximately 6.9918
- M = 650,000 x [0.0054167 x 6.9918] / [6.9918 - 1] = 650,000 x 0.037876 / 5.9918 = $4,108.44 per month
- Total repaid = $4,108.44 x 360 = $1,479,039
- Total interest = $1,479,039 - $650,000 = $829,039
How Interest Rates Affect Your Repayments
| Interest Rate | Monthly Payment (30 yr, $650k) | Total Interest |
|---|---|---|
| 5.0% | $3,489 | $606,163 |
| 5.5% | $3,691 | $678,626 |
| 6.0% | $3,897 | $752,948 |
| 6.5% | $4,108 | $829,039 |
| 7.0% | $4,324 | $906,808 |
| 7.5% | $4,545 | $986,162 |
Even a 1% increase in interest rate adds significantly to your total repayment over a 30-year term. This is why securing a competitive rate and making extra repayments where possible can save tens of thousands of dollars.
Loan-to-Value Ratio (LVR)
LVR is your loan amount expressed as a percentage of the property value. It is a key measure lenders use to assess risk. In New Zealand, the Reserve Bank limits the proportion of high-LVR lending banks can do. Most owner-occupier borrowers need at least a 20% deposit (80% LVR). Borrowers with less than 20% deposit may still get a loan, but typically pay a higher interest rate (low-equity premium) or need to meet stricter criteria.
LVR = Loan Amount / Property Value x 100
Making Extra Repayments
Making extra payments on top of your regular repayment can significantly reduce both the time to pay off your mortgage and the total interest you pay. Even small regular additional amounts compound over time. For example, paying an extra $200 per month on a $650,000, 30-year, 6.5% mortgage cuts nearly four years from the term and saves more than $100,000 in interest.
Most floating-rate mortgages in New Zealand allow unlimited extra repayments. Fixed-rate mortgages typically allow a limited amount of extra repayments each year without break fee penalties.
Fixed vs Floating Rates
New Zealand mortgage borrowers can choose between fixed rates (locked for 6 months to 5 years) and a floating (variable) rate that can change at any time. Fixed rates give certainty over repayments for the fixed period but typically carry break fee penalties for early repayment or refinancing. Floating rates allow unlimited extra repayments and flexibility but payments change when the bank adjusts its rate, typically following movements in the Official Cash Rate (OCR) set by the Reserve Bank of New Zealand.
Related Calculators
- Mortgage Calculators: all NZ home loan calculators in one place.
- Mortgage Repayment Calculator: compare repayment scenarios side by side.
- Mortgage Extra Repayment Calculator: see how extra payments cut your loan term.
- Mortgage Amortisation Schedule: full payment-by-payment breakdown.
- Mortgage Refinance Calculator: is it worth switching lenders?
Sources and method: Standard mortgage amortisation formula (principal, interest, amortisation). Reserve Bank of New Zealand LVR restrictions (rbnz.govt.nz). Interest rate comparisons are illustrative only; contact your lender for current applicable rates.
This calculator provides indicative estimates only. It does not account for lender fees, mortgage insurance, rate changes during the term, or other charges. Actual repayments will depend on your specific loan agreement. Always confirm details with your lender or a registered financial adviser.