See exactly how your NZ mortgage repayments split between interest and principal over the entire loan term, with an interactive chart you can explore year by year. Enter your loan details below and see how much of your money goes to the bank versus reducing your debt, how quickly you build equity, and how extra repayments can dramatically reduce your total interest cost.
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.
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.
Even small extra repayments have a large effect because they reduce the principal early in the loan when interest is calculated on the full balance. An extra $100 per fortnight on a $600,000 loan at 6.5% saves approximately $50,000-80,000 in interest and cuts 3-5 years from the loan term, depending on when you start. This is because the savings compound: a lower balance means lower interest each period, which means more of each payment reduces the principal, which further reduces the balance and so on. The visualiser shows you the exact saving for whatever extra amount you enter.
Switching from monthly to fortnightly repayments has a real but often misunderstood effect. With true fortnightly repayments (half the monthly payment paid every two weeks), you end up making 26 half-payments per year instead of 24 (12 months times 2). That is the equivalent of 13 monthly payments per year instead of 12, which adds up to roughly one extra full monthly payment per year. Over a 30-year loan this can save several years of payments and tens of thousands of dollars in interest. This effect is already calculated in the visualiser when you select fortnightly frequency.
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.
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.
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