Split Loan Calculator (AU)

What an Australian split loan is

A split home loan in Australia divides your mortgage into two (or sometimes more) portions, each on a different rate type. The most common structure: part of the loan on a fixed rate (typically locked for 2-5 years) and part on a variable rate (floats with the RBA cash rate and bank pricing decisions). You make one combined monthly payment, but each portion accrues interest separately.

Australia is one of the few markets where split loans are routine — perhaps 30-40% of new mortgages use some form of split. The structure exists because Australian banks aggressively price both fixed and variable products, and borrowers naturally hedge between certainty (fixed) and flexibility (variable). UK borrowers occasionally use similar structures via offset arrangements; US borrowers almost never split (different lending culture).

The math: each portion is treated as an independent loan. A 50/50 split on $500,000 produces a $250,000 fixed loan and a $250,000 variable loan, each with their own PMT calculation. The combined monthly payment is the sum. The blended effective rate is the weighted average of the two rates.

Why borrowers choose to split

Rate hedge against uncertainty

If you fix 100% and rates drop, you miss the benefit. If you go 100% variable and rates rise, your payment increases. Splitting lets you capture some of both worlds — half your payment is protected from rate rises (fixed portion), half can decrease if rates fall (variable portion). Insurance against being wrong about rate direction.

Flexibility on extra repayments

Fixed loans in Australia typically restrict extra repayments — often capped at A$10,000-30,000 per year, with break fees if you exceed it. Variable loans have no such restriction. By keeping a meaningful portion variable, you preserve the ability to pay down principal aggressively if your income improves or you receive a windfall.

Offset account compatibility

Offset accounts (where savings reduce interest charged on the loan) only work with variable loans in most banks. Many split borrowers keep enough loan in variable mode to absorb their expected offset balance. A borrower with A$50K in savings often keeps A$100-150K of loan as variable so the offset can absorb fully.

Investment property tax planning

Investment property mortgages have specific tax considerations. Some borrowers split between an interest-only investment portion (max tax deductibility) and a principal+interest owner-occupied portion. The split structure simplifies the accounting and maximizes the tax-deductible interest.

Choosing your split ratio

The conservative 70/30 (mostly fixed)

70% fixed, 30% variable. Optimizes for payment certainty — most of your monthly bill is locked in. The variable portion is large enough to absorb a moderate offset balance and allow some extra repayments. Best for risk-averse borrowers, recent home buyers stretching their budget, and anyone who would struggle with a 30%+ payment increase if variable rates spiked.

The balanced 50/50

The default choice for many. Half your loan benefits from any rate cut, half is protected from any rate rise. Mathematically neutral on rate direction. Good for borrowers with stable income who don’t have a strong view on rates and want exposure to both outcomes.

The aggressive 30/70 (mostly variable)

30% fixed, 70% variable. Maximizes flexibility — large offset capacity, generous extra repayment limits. Banks on rates falling or staying flat. Best for borrowers with significant savings (large offset balance), high incomes (can absorb rate rises), or strong conviction that rates will fall. Higher reward, higher risk.

The expert 0/100 or 100/0

Pure single-rate loans. Sometimes the right answer despite the split-loan marketing. If you have a very strong view on rates and limited need for flexibility, going pure on one side simplifies the loan and reduces fees. Most pure-variable borrowers do this when rates seem high (betting on falls); most pure-fixed borrowers do this when rates seem to be rising.

The downsides nobody mentions

You pay TWO sets of fees

Many lenders charge package fees per loan account. A split loan has two accounts, which can double the annual package fee from ~A$400 to ~A$800. Always check the fee structure — some banks waive the second account fee, others don’t.

The fixed portion is illiquid

Once you fix a portion, you can’t easily change your mind. Wanting to make a large extra repayment? Restricted to the variable side or pay break fees. Wanting to refinance? The fixed portion charges break costs that can be A$5K-30K+ depending on rate movements and remaining fix term.

Refixing creates complexity

When the fixed period ends (typically 2-5 years), the fixed portion reverts to variable rate (often higher than market). You then have to decide: refix at current rates, keep variable, or restructure entirely. Many borrowers don’t act and end up paying inflated revert rates for months.

Banks profit from confusion

Split loans are more profitable for banks than single loans because borrowers compare less effectively across products. You end up comparing your fixed rate against competitor fixed rates AND your variable against competitor variable AND the combined math gets complex. Many borrowers stay with their bank longer than they should because comparison feels difficult.

“Just refinance” is harder

Refinancing a split loan to another bank often requires unwinding both portions, which can mean break fees on the fixed side. The cost of refinancing scales with the size of the fixed portion and how much rates have moved against you.

Split Loan Calculator FAQ

Can I split into more than two portions?

Yes — most AU banks allow up to 4-6 splits. The most common are 3-way splits: short fixed (1-2 years), medium fixed (3-5 years), variable. This staggers rate exposure across multiple terms. The math gets messier but the principle is the same: each split is an independent loan with its own rate and PMT calculation.

What’s a typical break fee on a fixed portion?

Depends on remaining fix term and rate movement. If rates have risen since you fixed (bank’s “cost” of you breaking is low), break fees are minimal. If rates have fallen (bank loses by you breaking), fees can be A$5K-30K+ on a A$250K fixed loan with 3+ years remaining. Always request a break fee quote before deciding.

Does the calculator handle the rate change after the fixed period ends?

No — it shows the math for the initial loan structure. After the fixed period ends (typically 2-5 years in), the fixed portion reverts to a “revert variable” rate that’s usually higher than the original variable. You’d then need to re-run the calculator with the new rate. Most borrowers refix or refinance at this point.

How does offset interact with the split?

Offset only works against variable portions in most banks. If you have $50K offset balance and a 50/50 split on a $500K loan ($250K variable / $250K fixed), the offset reduces interest charges on $50K of the variable side — effectively reducing your variable balance to $200K from an interest perspective. The fixed portion is unaffected.

Should I split if I’m planning to sell in 2-3 years?

Generally no. The transaction costs of setting up a split, plus break fees when you sell within the fixed term, often outweigh the benefits. Short-hold borrowers usually do better with a pure variable loan with no break-fee exposure.

What if my income changes during the fixed period?

Variable portion absorbs the change first. If income drops, you can reduce extra repayments on the variable side. If income rises, you can pay extra into variable (or offset). The fixed portion stays the same regardless. This insulating effect is one of the main reasons borrowers split.