Fixed vs Floating: How to Structure Your Mortgage in 2026

There's a persistent myth that mortgage structure decisions come down to predicting where interest rates are headed. Homeowners agonise over whether to fix or float, desperately trying to read economic tea leaves and outsmart the market. Here's the uncomfortable truth: even professional economists with access to sophisticated models and decades of experience get interest rate predictions wrong with remarkable consistency. If they can't reliably forecast where rates are going, what hope do you have?

The good news is that structuring your mortgage well doesn't actually require a crystal ball. It requires understanding your own financial situation, your tolerance for uncertainty, and how to use the tools available to create a loan structure that works regardless of what the economy decides to do next.

Understanding What You're Actually Choosing Between

A fixed rate mortgage is exactly what it sounds like: you lock in an interest rate for a specified period , typically anywhere from six months to five years , and your repayments stay constant for that duration. When the term ends, you either fix again at whatever rates are available or roll onto a floating rate.

A floating rate moves up and down with market conditions. When the Reserve Bank adjusts the Official Cash Rate, your floating rate will typically follow within a few weeks. This means your repayments can change with relatively little notice, for better or worse.

The mistake most people make is treating this as an either/or decision when it's really a spectrum.

The Case for Splitting Your Mortgage

Here's where things get more interesting. There's no rule saying your entire mortgage must be on a single rate type or term. In fact, splitting your loan across multiple portions is one of the most sensible things you can do, yet many homeowners don't realise it's an option.

A split mortgage might have one portion fixed for two years, another fixed for three years, and a smaller floating or revolving credit portion for flexibility. This approach offers several advantages that a single-structure loan simply cannot match.

Revolving Credit: The Misunderstood Tool

Speaking of flexibility, let's address revolving credit facilities, which are simultaneously one of the most useful and most abused mortgage features available.

A revolving credit facility works like a giant overdraft secured against your property. You have a limit , say, $50,000 , and your salary gets paid directly into it, reducing the balance and therefore the interest charged. You draw on it for expenses throughout the month, and ideally, the balance trends downward over time.

For disciplined borrowers, revolving credit is genuinely powerful. Every dollar sitting in the account reduces your interest, and you maintain complete flexibility to access funds when needed. There are no fixed repayments forcing a particular schedule , you control the pace.

Be honest with yourself about which category you fall into. If you've ever let a credit card balance creep up because the available limit felt like "your money," a large revolving credit facility probably isn't for you. There's no shame in choosing a structure that protects you from your own tendencies.

How Much Should You Keep Floating?

A common rule of thumb suggests keeping between 10% and 20% of your mortgage on a floating or revolving basis, with the remainder fixed across varying terms. This provides enough flexibility to make meaningful extra payments when possible while protecting most of your loan from rate volatility.

However, rules of thumb are just starting points. Your ideal split depends on factors specific to your situation:

• Variable income: If you're self-employed, work on commission, or receive irregular bonuses, a larger floating portion lets you make bigger payments during good months without being locked into commitments you can't sustain during lean periods.
• Expecting a cash injection: If you're expecting to sell another property, receive an inheritance, or have maturing investments, having floating capacity to absorb that money makes sense.
• Certainty matters most: If predictability matters more to you than optimisation, weighting heavily toward fixed rates lets you sleep at night knowing exactly what your repayments will be.
• Tight finances: If your financial situation is tight and you need every dollar accounted for, a fully fixed structure with set repayments might actually serve you better than flexibility you can't afford to use.

The Term Length Question

Assuming you're fixing at least part of your mortgage, the question becomes: for how long? Six months? One year? Five years? Something in between?

Shorter terms typically offer lower rates but require more frequent renewals and expose you to rate changes sooner. Longer terms provide extended certainty but usually at a premium, and you're locked out of falling rates if they drop.

The longest terms (four and five years) suit borrowers who prioritise certainty above all else and are willing to pay for it. They're also worth considering when rates are historically low and you want to lock in that position for as long as possible , though identifying "historically low" in the moment is harder than it sounds.

Building a Structure That Survives Contact With Reality

The best mortgage structure isn't the one that would perform perfectly if you could predict the future. It's the one that performs adequately across a range of possible futures while matching how you actually manage money.

Before your next mortgage review, spend some time thinking about your genuine priorities. Consider how much payment certainty matters to you, whether you are likely to make extra payments or if that is aspirational thinking, what your realistic timeline in this property is, and how you would cope if rates moved significantly in either direction. Armed with honest answers to those questions, you can have a far more productive conversation with your lender or mortgage adviser about structuring your loan. You'll be making decisions based on self-knowledge rather than rate speculation.

Your Mortgage Structure Should Evolve

What works for you today might not work in five years. A mortgage structure suited to a young couple with variable income and no children might be entirely wrong for that same couple once they have kids, stable careers, and different priorities.

Treat your mortgage reviews as opportunities to reassess not just the rates on offer but the fundamental structure of your loan. As your life changes, your mortgage should change with it. The homeowners who do this consistently , who treat their mortgage as an active financial tool rather than a static obligation , invariably end up in a stronger position than those who set and forget.