Choosing fixed or floating is less about guessing the next OCR move and more about which risk you prefer to carry: rate movement risk, or break-cost and flexibility risk. Plenty of households split the loan across both for that reason.
What fixed buys you
A fixed rate holds your repayment steady for a set term — often one to five years. That certainty helps budgeting. The trade-off is break costs if you repay early, refinance, or sell in a way that breaks the fixed period, and tighter limits on extra repayments during the fix.
What floating buys you
A floating (variable) rate can move up or down. Extra repayments and lump sums are usually easier. You carry the risk that repayments rise when rates rise. Some products blend floating with revolving credit or offset features.
Break costs are the fine print that matters
If you fix and then need to change the loan, the break cost can be material. Before you fix the whole mortgage, ask what happens if you receive a lump sum, need to move, or want to refinance. The cheapest headline rate is a poor bargain if it traps you.
The mechanism is worth understanding because it explains when the cost is large and when it is nearly nothing. A break cost broadly compensates the lender for the difference between the rate you agreed and what it can now earn lending that money for your remaining fixed period. If wholesale rates have fallen since you fixed, that difference is real and you pay for it. If rates have risen, the lender is not worse off and the charge is typically small or zero. This is why the same decision to break can be free in one year and painful in another, and why no general rule about breaking fixed loans is reliable — you have to ask for the actual figure.
The choice is usually about your next few years, not the market
The most useful question is not where rates are heading but how likely your circumstances are to change. Someone who might be transferred for work, is planning to start a family on one income, or expects an inheritance or a bonus has a genuine reason to value flexibility. Someone settled in a job and a house, with a budget that has no slack in it, is buying something valuable when they buy certainty. Neither is a prediction. Both are honest readings of the household's own risk.
Split loans
Many borrowers fix a core portion for certainty and leave a slice floating for offset, extra repayments, or an expected bonus. That is a structure decision, not a forecast.
Splitting the fixed portion across different maturities is a related idea. If the whole loan comes off a fixed rate on one date, that date carries all your refix risk. Staggering it so that portions mature at different times means a rate rise only ever hits part of the balance at once, which smooths the shock without requiring anyone to be right about timing. The cost is a slightly more complicated loan and, sometimes, a marginally worse rate on smaller tranches.
How to use the calculator
FinLab models one rate across the term so you can see repayment shape, total interest, and the effect of extras or offset. Run the rate you have been quoted, then run a rate two points higher. The second run is a private serviceability check. For advice on product structure, speak with a licensed adviser or your lender — FinLab is general information only.