See the two phases of a fixed and variable mix
A split loan divides one borrowing amount between fixed and variable rates. This calculator estimates the combined monthly payment during the fixed period, then rolls both projected balances into one payment at an assumed post-fixed rate. It helps make the transition visible rather than treating the starting payment as permanent.
A split is a product structure, not automatically a better outcome than fully fixed or fully variable borrowing. Fixed-rate break costs, package conditions, offset availability, redraw rules and future rates can matter. Use this as a scenario check alongside current lender documents and a broader household budget.
How to read the results
Initial combined repayment is the sum of separate principal-and-interest payments for the fixed and variable portions, each amortised over the full original term. The fixed portion is the nominated percentage of total loan; the rest is modelled at the variable rate.
Projected post-fixed repayment uses both balances after the fixed period, the entered revert rate and the remaining term. Payment shock is the post-fixed repayment less the initial combined repayment. It is an illustration only: it does not calculate a complete two-phase interest total.
Worked example
With the defaults, a $650,000 loan is split 50/50: $325,000 fixed at 6.09% and $325,000 variable at 6.49%, over 30 years. The fixed payment is about $1,967 and the variable payment about $2,052, producing an initial combined repayment of $4,019 a month.
After the three-year fixed period, the modelled balances total about $625,809. At the assumed 6.79% revert rate over 27 years, the projected payment is $4,219 a month, a $200 monthly increase.
Assumptions and limitations
- The fixed percentage determines the initial dollar allocation between the two portions.
- Both portions make monthly principal-and-interest repayments over the original term.
- The variable rate remains unchanged during the entered fixed period.
- At the end of that period, both projected balances use one entered revert rate.
- Fees, offsets, redraws, extra repayments, break costs and future rate movements are excluded.
Frequently asked questions
Does the variable portion change rate in this calculation?
No. It remains at the entered variable rate during the fixed period; real variable rates can move at any time.
Why is there one payment after the fixed period?
The model combines the two projected balances and amortises them together at the assumed revert rate for the remaining term.
Can the fixed period be the entire loan term?
No. It must be shorter than the total term because the calculator is specifically estimating the post-fixed phase.
This calculator and supporting information provide general estimates only. They do not take account of every product rule, tax consequence or personal circumstance and are not financial, tax, credit or legal advice.