You are staring at two numbers on a loan comparison table, and the bank wants an answer by settlement. Fixed or variable is not really a bet on where interest rates are headed next. Nobody, including your bank, reliably knows that. It is a choice about how much certainty you want in your monthly budget, and how much flexibility you are prepared to give up to get it.
What fixing actually locks in
A fixed rate holds your interest rate steady for an agreed period at the start of the loan. Whatever happens to the broader market during that time, your rate and your repayment amount do not move. For a household working out what it can actually afford each month, that predictability is the whole appeal. You can build a budget around a fixed number and know it will not change until the fixed term ends, at which point the loan typically reverts to a variable rate or you choose to fix again.
That certainty is genuine, but it is also narrow. It only covers the fixed period. The next rate decision is still waiting at the end of the term.
What a variable rate gives you
A variable rate moves with the market. When lenders adjust their rates, your repayments adjust too, in both directions. That cuts both ways: if rates fall, your repayments can fall with them, without you having to do anything. If rates rise, so do your repayments, and your budget has to absorb that.
Variable loans typically also come with flexibility features, an offset account and the ability to make extra repayments are the two most common. We cover how those actually work, and how they differ from each other, in our guide to offset accounts and redraw, so we will not re-run the mechanics here. A fixed loan can restrict or exclude these features, which is the trade-off the next section covers.
The flexibility you trade when you fix
This is the part that catches people out, because it is not on the headline rate at all. Fixed-rate loans can cap how much extra you can repay during the fixed period, and offset or redraw features may be unavailable or limited to a variable portion of the loan. If you come into money and want to put it toward the mortgage, a fixed loan may only let you do that up to a limit before extra fees apply.
The other cost is exiting early. If you sell the property, refinance, or otherwise pay out a fixed loan before the fixed term ends, the lender can charge what is generally called a break cost, to cover its own position on the fixed-rate arrangement. How that cost is calculated, and how large it can be, depends on your lender and on what has happened to rates since you fixed. It is not a flat fee, and it is worth understanding as its own topic before you fix, not after. The practical takeaway for now is simpler: fixing trades some of your flexibility to exit or restructure the loan for certainty over your repayments.
Splitting the difference
You do not have to choose one or the other for the whole loan. A split loan divides your borrowing into a fixed portion and a variable portion, each behaving according to its own rules. The fixed portion gives you a steady, budgetable chunk of repayment. The variable portion still moves with the market, but it also still carries the offset and extra-repayment features described above, so you retain some ability to get ahead and access funds if you need to.
A split does not eliminate the trade-off. It lets you set how much of it you want. A larger fixed share means more certainty and less flexibility; a larger variable share means the reverse. Most lenders let you choose the proportions, so this is a genuine dial rather than a fixed even split.
How to decide without predicting rates
Do not try to time this. Instead, ask yourself two separate questions. First: how much would a change in your repayment actually disrupt your household budget, and how much do you value knowing the number in advance? That points you toward fixing some or all of the loan. Second: how likely are you to want to make large extra repayments, redraw savings through an offset, sell, or refinance during the period you are considering fixing? That points you toward staying variable, or keeping a variable portion.
Read the specific terms before you commit either way, as well as the rate. Ask your lender directly what the fixed-rate repayment limits are, whether offset is available on any portion, and how break costs are calculated if you would exit early. ASIC's Moneysmart guidance on choosing a home loan and on fixed versus variable rates is a good, lender-neutral place to check those mechanics before you sign. The right structure is the one that matches how you actually expect to use the loan, not a guess about where rates go next.