Mortgage Repayment Visualiser NZ 2026
This calculator shows exactly how a New Zealand mortgage repayment splits between interest and principal over the full loan term, so you can see where your money actually goes. Enter your loan amount, annual interest rate, loan term, and how often you repay (weekly, fortnightly or monthly), then add an optional extra repayment per period to see what a bit more would save. It returns your regular repayment, the total amount paid back, the total interest cost, and interest as a percentage of the loan; add extra repayments and it also shows the interest saved and how many years the loan is shortened by. An interactive chart lets you switch between a stacked view of interest versus principal paid each year, a line chart of the same figures, an equity growth curve, and a total-cost split showing principal against interest paid to the bank. Below the chart, a year-by-year amortisation table breaks down the annual payment, interest paid, principal paid, remaining balance and equity percentage for every year, and marks the crossover year when the principal portion of your payment first overtakes the interest portion. Use it to compare fixed-rate scenarios, test how extra repayments shorten your loan, or understand why the early years of a mortgage feel so interest-heavy. Figures are estimates for planning purposes and will differ slightly from your bank's exact calculations.
What the chart shows
In the early years of a mortgage, the vast majority of each repayment goes to paying interest, with only a small fraction reducing the actual loan balance (the principal). Over time this ratio shifts: as the balance falls, the interest charged each period falls too, so more of each payment goes toward principal. The stacked chart makes this shift visible. The line chart shows the absolute amounts of interest and principal paid each year. The equity view shows your ownership percentage growing over the loan term.
Why the interest bill is so large
On a $650,000 NZ home loan at 6.5% over 30 years, the total interest paid exceeds the original loan amount. This is not unusual: at a 6% or higher interest rate, a 30-year mortgage will cost you roughly as much in interest as the original loan itself. This is why the total cost column in the visualiser often surprises people. The loan is affordable on a monthly or fortnightly basis, but the full lifetime cost is much higher than the purchase price alone.
The power of extra repayments
Even small extra repayments have a large effect because they reduce the principal early in the loan, when interest is charged on the full balance. Take the default settings on this page: a $650,000 loan at 6.5% over 30 years repaid fortnightly. The regular repayment is $1,895.31 and the total interest over the term is $828,342.22. Add an extra $100 a fortnight and the total interest falls to $695,891.39, a saving of $132,450.82, and the loan is cleared in 26 years instead of 30. The saving compounds: a lower balance means less interest that period, so more of the next payment goes to principal, which lowers the balance again. The visualiser shows you the exact saving for whatever extra amount you enter, and the saving is larger the earlier in the loan you start.
Fortnightly vs monthly payments
Switching from monthly to fortnightly repayments is often described as a free way to shorten a loan, but that only holds if you keep paying half the monthly amount every fortnight. This visualiser does what most NZ banks do when they quote a fortnightly figure: it works out a true fortnightly repayment spread over the term you enter. Changing the frequency on its own therefore does very little. On the default $650,000 at 6.5% over 30 years, total interest is $829,039.17 paying monthly and $828,342.22 paying fortnightly, a difference of $696.96, and both schedules still run the full 30 years.
The acceleration comes from paying more, not from paying more often. Half the monthly repayment of $4,108.44 is $2,054.22, which is $158.91 above the fortnightly repayment of $1,895.31, and there are 26 fortnights in a year rather than 24 half-months, so you pay the equivalent of 13 monthly repayments instead of 12. You can model that here: select fortnightly and enter $158.91 in the extra repayment box. The loan is then repaid in 25 years instead of 30 and total interest drops to $638,109.13, a saving of $190,233.08 against the fortnightly baseline.
The principal-interest crossover
The crossover point is the year in which the principal portion of each payment first exceeds the interest portion. Before this point you are paying more to the bank than to yourself; after it, more of each payment reduces what you owe. For a standard 30-year NZ mortgage at typical interest rates, the crossover happens roughly in years 15 to 20. Extra repayments bring it forward significantly. The visualiser marks this crossover year in the chart and the table.
NZ mortgage context
Most NZ home loans are fixed-rate for an initial period (typically 1 to 5 years) and then refix. The interest rate you enter in this visualiser should be the rate for your current fixed period; change it to see how your picture changes if you refix at a higher or lower rate. The mortgage repayment calculator shows your regular repayment amount, and the mortgage break fee calculator estimates the cost of breaking a fixed-rate loan early.
Related tools and guides
- Mortgage repayment calculator: repayments on a given loan.
- Amortisation schedule: the full payment-by-payment breakdown.
- Mortgage repayment strategies: what actually shortens a mortgage.