Split Loan Calculator
Enter your loan amount, two interest rates and the split percentage to see the blended rate and combined monthly repayment. This is an estimate only and does not constitute credit advice or an offer of credit.
Is that number right for your situation?
A calculator applies one formula. Lenders apply their own, and they disagree with each other. Send us what you worked out and we will tell you how it looks against real lender policy.
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How this is calculated
A split loan divides your mortgage into two portions: one fixed and one variable. The fixed portion has a rate that stays constant for an agreed period (commonly 1–5 years), giving you repayment certainty. The variable portion moves with the market, giving you flexibility — including the ability to make unlimited extra repayments and use an offset account.
The calculator splits your loan amount according to the percentage you specify. For each portion, it calculates the monthly repayment using the standard amortisation formula at that portion's rate. The blended rate is a simple weighted average: (fixed rate x fixed percentage + variable rate x variable percentage) / 100. The combined repayment is the sum of the two portion repayments.
After the fixed period ends, the fixed portion typically reverts to the lender's standard variable rate — which may be higher or lower than the rate you had. At that point you can choose to re-fix, switch to fully variable, or split again. This calculator models the initial period only.
What this doesn't account for
- Fixed period reversion. When the fixed period ends, the rate changes. This calculator shows the blended rate for the fixed period only, not the reverted rate.
- Different fixed terms. You might fix for 1, 2, 3 or 5 years. The longer the fix, the longer you have rate certainty — but the higher the risk of break costs if you need to exit early.
- Break costs. Breaking a fixed-rate loan early can trigger substantial break costs, especially if rates have fallen since you fixed. The variable portion has no such restriction.
- Offset and extra repayments. Offset accounts and unlimited extra repayments typically only work on the variable portion. The fixed portion may have caps on extra repayments. This affects the effective cost over time.
- Fees. Some lenders charge a split fee or require a package fee for split loans. These aren't included in the calculation.
Common questions
Splitting gives you a balance of certainty and flexibility. The fixed portion protects you from rate rises and gives you predictable repayments. The variable portion lets you benefit from rate cuts, make unlimited extra repayments, and use an offset account. It's a hedge against not knowing which way rates will go — you win on one portion and lose on the other, but the swings are smaller.
There's no universal answer. If you're more concerned about rate rises, fix a larger portion (70–80%). If you want flexibility and plan to make extra repayments, keep more variable (50–60%). A 50/50 split is a common middle ground. Think about your risk tolerance, how much extra you plan to pay, and how long you intend to hold the loan.
You can usually change the split when the fixed period ends, or by refinancing. During the fixed period, changing the fixed portion typically triggers break costs. Some lenders allow you to increase the variable portion by paying down the fixed side, but this may also incur costs. We'll explain the rules for any loan we recommend.
The blended rate is useful for comparing a split loan against a single-rate alternative. If the blended rate is lower than a fully variable option, the split is ahead on rate — but remember the fixed portion limits flexibility. The comparison rate (which includes fees) is a better like-for-like measure, and we'll show you that for any loan we recommend.
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