Mortgage Refix Strategy Calculator
Compare 1, 2, 3 and 5-year fixed mortgage terms side-by-side to see which gives the lowest total cost over your full loan term.
About this calculator
This calculator implements RBNZ retail mortgage rate series from Reserve Bank of New Zealand. Last consulted 18 May 2026. Verify the figures yourself by following the link.
NZ mortgage rates (mid-2026)
Indicative across major banks- •1-year fixed: ~6.40–6.55%
- •2-year fixed (most popular): ~6.15–6.35%
- •3-year fixed: ~6.10–6.30%
- •5-year fixed: ~6.30–6.50%
- •Floating: ~7.85%
- •RBNZ OCR (review 8-weekly): 2.25%
Source: RBNZ — Retail mortgage rates
Disclaimer
This calculator provides estimates for general information purposes only. Results should not be relied upon as professional financial, tax, or legal advice. Tax rates and thresholds are based on publicly available IRD data and may change. Always consult a qualified tax agent or financial adviser for advice specific to your circumstances.
How NZ mortgage refix strategy works
Compare the lifetime cost of fixing for different terms, then reverting to the post-fix market rate.
- 1
Initial fixed payment
P_fix = P × r ÷ 12 × (1 + r ÷ 12)^n ÷ ((1 + r ÷ 12)^n − 1)
Standard amortising payment formula.
- 2
Balance after fix period
Balance = P × (1 + r ÷ 12)^k − P_fix × ((1 + r ÷ 12)^k − 1) ÷ (r ÷ 12)
k = months of fix period.
- 3
Post-fix payment
P_post = Balance × r_post ÷ 12 × (1 + r_post ÷ 12)^m ÷ ((1 + r_post ÷ 12)^m − 1)
m = remaining months. r_post is your assumed post-fix rate.
- 4
Total lifetime cost
Total_cost = P_fix × k + P_post × m
Compare totals across 1/2/3/5-yr fixes.
Worked example
Inputs: $650k, 25y, current 2yr 6.25%, assumed post 6.20%
Result: 2-yr fix total ~$1.27M. 3-yr fix slightly less if curve declines.
Frequently Asked Questions
Which fixed term is best for a NZ mortgage?
Can I split my mortgage across multiple fixed terms?
What is mortgage refix and when does it happen?
Can I break my fixed mortgage early to refix at a lower rate?
The mortgage refix strategy calculator compares fixing your NZ home loan for 1, 2, 3, or 5 years side-by-side, projecting the total cost of each strategy over the full loan term including the rate you expect after the fix ends.
How this calculator works
Choosing a fixed term is a bet on where rates go next, and the cheapest advertised rate is not automatically the cheapest strategy. For each term the calculator computes the standard amortising repayment at that term's rate, tracks the remaining balance to the end of the fix, then re-amortises the balance at your assumed post-fix rate for the remaining years. Comparing the lifetime totals shows how much a lower short-term rate is really worth against the certainty of a longer fix. As a rule of thumb, a shorter fix wins if rates fall by more than the gap between the two rates before you refix; a longer fix wins if rates rise or stay flat. Most NZ borrowers split the loan into two or three tranches with staggered maturities to smooth the risk — the calculator lets you compare each tranche's strategy explicitly.
Indicative NZ mortgage rates (mid-2026)
| 1-year fixed | ~6.40 - 6.55% |
| 2-year fixed (most popular) | ~6.15 - 6.35% |
| 3-year fixed | ~6.10 - 6.30% |
| 5-year fixed | ~6.30 - 6.50% |
| Floating | ~7.85% |
| RBNZ OCR | 2.25% (reviewed ~every 6 weeks) |
Advertised specials move weekly; use your actual bank quotes in the calculator.
Worked Examples
$650,000 over 25 years: 2-year fix at 6.25%, assuming ~6.20% after the fix
Lifetime cost ≈ $1.27M; a 3-year fix at a similar rate costs almost the same — certainty is cheap here.
- Repayment at 6.25%: ≈ $4,288/month
- Balance after the 2-year fix: ≈ $625,000
- Re-amortised at 6.20% for 23 years: ≈ $4,270/month
- Total ≈ $1.27M over the life of the loan
$500,000 over 30 years: 1-year fix at 6.45% vs 2-year fix at 6.25%
The 1-year fix costs ≈ $780 more in year one — it only wins if rates drop by more than ~0.2% before you refix.
- Repayment at 6.45%: ≈ $3,144/month
- Repayment at 6.25%: ≈ $3,079/month
- Year-one difference: ($3,144 − $3,079) × 12 ≈ $780
- Break-even: the 1-year refix rate must be ~0.2%+ below 6.25% to recover the difference
Built and maintained by Konstantin Iakovlev. Data sourced from the IRD and official New Zealand government sources.
Last reviewed: