Finance & business New Zealand
Extra Repayments Calculator New Zealand
Paying a little more than the minimum on a home loan can take years off it, because every extra dollar goes straight against the balance. Enter your balance, rate and years left, plus an extra monthly amount or a lump sum, to see the interest and time you would save.
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Interest saved
—Minimum repayment each month
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Years to repay as is
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Years to repay with extras
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Time saved
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Interest paid as is
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Interest paid with extras
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The comparison
An estimate, not advice. General information and estimates only, not financial advice. Rates, fees and rules change, so check the lender's own terms and speak to a licensed adviser before you act.
How much do extra mortgage repayments save?
On a $600,000 loan at 5.6% with 25 years left, adding $300 a month and a $10,000 lump sum now cuts about 4.2 years off the loan and saves around $109,052 in interest. The earlier the extra goes in, the more it saves.
How extra repayments work
A home loan repayment is split between interest and principal. Early in the loan most of it is interest. An extra payment is all principal, so it cuts the balance that interest is charged on from then on, and the saving compounds for the rest of the term.
That is why the same extra dollar saves more interest in year two than in year twenty.
Fixed rates and limits
Most New Zealand home loans are split between fixed and floating portions. Fixed portions often allow only limited extra payments before a break fee applies, while floating portions and revolving credit accounts allow extra payments freely. Some borrowers put extras on the floating portion first, or make lump sums at the end of a fixed term when the rate resets.
Ask your lender what the limit is and whether payments are applied immediately.
To compare rates, use the refinance calculator.
How this is calculated
The rule, step by step, so you can check any figure by hand.
monthly repayment = loan × r ÷ (1 − (1 + r)^−n), with r = rate ÷ 12each month: interest = balance × r, then balance = balance + interest − repayment − extraa lump sum is taken off the balance at the startinterest saved = interest as is − interest with extrastime saved = months as is − months with extras
The saving comes from interest being charged on a smaller balance every month afterwards, so money paid early saves the most. A lump sum now is worth much more than the same money paid in the last few years of the loan.
In New Zealand many borrowers are on a fixed rate for one to five years, and lenders often limit how much extra you can pay during the fixed term without a break fee. Floating rates and revolving credit have no such limits, so check your loan terms before you rely on the saving.
A worked example
A $600,000 loan at 5.6% with 25 years left, an extra $300 a month and a $10,000 lump sum now.
- Minimum repayment$3,720.44
- Years to repay as is25.0
- Years with the extras20.8
- Interest as is$516,133
- Interest saved$109,052
About 4.2 years sooner and $109,052 less interest.
Even a small regular amount adds up over a long loan.
Weekly and fortnightly payments
Paying fortnightly instead of monthly means 26 half-payments, or 13 full months, in a year rather than 12. That is a built-in extra repayment, though the benefit depends on how your lender applies the payments. Use the mortgage calculator to compare frequencies.
What it leaves out
Rate changes at refix time, fees and offset or revolving credit balances are not modelled. Re-run the calculation when your rate changes.
What this calculator does not do
- Constant rate for the whole loan
- Monthly payments
- Lender limits on extras not modelled
- An estimate, not advice
Common questions
How much can extra repayments save?
On a long loan, tens of thousands of dollars in interest and several years off the term.
Is a lump sum better than regular extras?
A lump sum now saves more than the same amount paid later.
Can I pay extra on a fixed rate?
Often only up to a limit without a break fee. Check with your lender.
Do fortnightly payments help?
They make the equivalent of an extra month's payment each year.
Does the rate stay constant?
In this calculation, yes. Re-run it when your rate changes.
Where these numbers come from
- Sorted — Retirement Commission money guidance Independent guidance on borrowing, saving and debt
Method last reviewed 2026-10-28 This calculator uses fixed rules rather than rates that change, and its method is re-checked against the sources above at least once a year. Out of date? Tell us and we will fix it.
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