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Fixed vs variable (and split) home loan calculator.

A fixed rate locks your repayment for a set period, a variable rate moves with your lender, and a split loan does a bit of both. Enter your loan, the fixed and variable rates on offer, the fixed period and the share you would fix, and the calculator compares total repayments and interest over the fixed period for all three.

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How this calculator works.

  1. Each option’s monthly repayment is the principal & interest repayment for its rate, sized over a 30-year loan.
  2. Over the fixed period the calculator adds up the repayments and works out the interest as the repayments less the principal repaid.
  3. The variable rate can be nudged up or down with the expected change slider. The change is applied from the first month for the whole period, so it is a what-if rather than a forecast.
  4. A split loan puts your chosen share at the fixed rate and the rest at the variable rate, and adds the two together.
  5. The cheapest of the three over the fixed period is highlighted, along with how much it saves against the most expensive.

What it assumes

  • The starting rates are 6.44% variable and 6.19% fixed, with a 3-year fixed period and a 50% fixed share for the split.
  • Loan term for repayment sizing: 30 years.
  • The comparison stops at the end of the fixed period. What happens to the rate afterwards is not modelled.
  • Assumptions last reviewed 25 September 2026.

Questions people ask.

Should I choose a fixed or variable rate?

The calculator shows which is cheapest for the rates and rate change you enter (with the starting numbers, all fixed over 3 years), but the choice also depends on how much certainty you want and what features you need. A fixed rate gives predictable repayments; a variable rate is usually more flexible. A broker can help you weigh them for your situation.

What is a split loan?

A split loan divides your borrowing into a fixed portion and a variable portion. You get some certainty on the fixed part and keep flexibility, such as extra repayments or an offset, on the variable part.

What happens when my fixed rate ends?

Most loans revert to the lender’s variable rate unless you fix again, and the reversion rate can be higher than a rate you could get elsewhere. This calculator covers the fixed period only.

Can I make extra repayments on a fixed loan?

Often only up to a limit each year. Offset accounts and unlimited extra repayments are more common on variable loans, so check what your fixed option allows.

What if I need to leave a fixed loan early?

You may owe a break cost. The fixed-rate break cost calculator gives an indicative figure.

More calculators.

Fixed vs Variable (and Split) Home Loan Calculator | Siare