Extra mortgage repayments calculator
See how much time and interest you save by paying a little more each time or by making a lump sum, and how much extra a fixed rate allows without a break fee.
The short answer
On a $500,000 loan at 5.06% over 30 years, paying $100 more every month and a $20,000 lump sum after the first year clears the loan 4 years 6 months sooner and saves $96,207 in interest.
| Regular repayment | $2,702.48 |
| Plus extra each time | $100.00 |
| $20,000 lump sum after year 1 | $20,000 |
| Paid off without extras | 30 years · 10 November 2056 |
| Paid off with extras | 25 years 6 months · 10 May 2052 |
| Interest without extras | $472,887 |
| Interest with extras | $376,680 |
| Interest saved | $96,207 |
Balance owing, with and without extras
- Without extras
- With extras
On a fixed rate, BNZ and Kiwibank let you repay up to 5% extra a year without a break fee; on this loan 5% is $25,000. Your extra works out at $23.08 a week, more than the $250 a week increase ANZ allows on a fixed rate.
Both runs use the same regular repayment. A lump sum is paid straight after the last repayment of the year you choose. Repayments are rounded up to the cent (banks do not publish their rounding), so the last repayment is a little smaller. The rate is assumed to stay the same for the whole term.
How much extra can you pay on a fixed rate?
On a floating rate you can repay extra at any time. On a fixed rate, banks allow some extra each year without a break fee. These are the limits we found on the banks’ own pages, accessed 10 November 2026.
| Bank | Allowance during a fixed term | Source |
|---|---|---|
| ANZ | Increase your regular repayments by up to $250 a week (first increase each year), plus one lump sum a year of up to 5% of the current loan amount. The year runs from the start of the fixed period or its anniversary. | ANZ, 10 November 2026 |
| BNZ | Up to an extra 5% of your loan balance each year on a fixed Standard home loan. | BNZ, 10 November 2026 |
| Kiwibank | Up to 5% of the loan amount at the start of the fixed term in any year, by higher repayments or lump sums. | Kiwibank, 10 November 2026 |
We could not confirm ASB’s or Westpac’s allowance this time, so we do not list one. Check with your bank before paying extra on a fixed rate.
Lump sums: shorter loan or lower repayment?
After a lump sum, banks usually keep your repayment the same, so the loan finishes sooner and you save the most interest. You can ask for a lower repayment over the same term instead. Our calculator does either.
An example from ANZ
ANZ’s handbook gives this example: on a $400,000 loan over 30 years at 4.00%, an extra $30 a week from the start pays it off in 26 years 7 months and saves $37,727 in interest. Our engine reproduces the time exactly and the interest to within 0.3%.
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Other repayment questions
Fixed or floating
Your repayment at every term, refixing and split loans.
Open →Break fee
An estimate of the fee for leaving a fixed rate early.
Open →Interest only
What interest only costs, against table and reducing loans.
Open →Mortgage rates
Every big bank’s advertised rates, dated, with the OCR.
Open →Repayment calculator
What will your repayments be?
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