Getting the Most From a Home Loan Refinance Calculator: Tips and Common Errors

Updated 20 July 2026 · Property and home loans

A Home Loan Refinance Calculator gives a fast answer, but the answer is only as good as what goes in. These are the mistakes we see most often with home loan refinance calculations in Australia, and how to avoid them.

1. Borrowing the maximum

Lenders test you at a higher rate, but your budget still needs room for rate rises, repairs and life changes.

2. Forgetting purchase costs

Stamp duty, conveyancing, inspections and moving can add several percent to the price.

3. Comparing headline rates only

Fees, offset accounts and flexibility on extra repayments can matter as much as the rate.

4. Assuming prices always rise

Property growth varies by location and period. Plan for flat or falling prices too.

5. Overlooking the detail that matters most here

Ask your current lender for a rate cut first. A phone call is often enough to get a better deal.

How the monthly saving changes with current rate

A common mistake is getting one input slightly wrong. Here is what happens to the monthly saving when “Current rate (%)” is off by up to 20% in either direction, with everything else held steady.

Current rate (%)	Monthly saving
5.2	-$209.50
5.85	-$15.20
6.5	$185.02
7.15	$390.87
7.8	$602.06

At 5.2 the result is -$209.50; at 7.8 it is $602.06. If a small change in this input moves the answer a lot, it is worth double-checking that figure before you rely on the result.

A quick sense check

Saving = current repayment − new repayment. Break-even = switching costs ÷ monthly saving. With typical inputs the calculator returns monthly saving of $185.02. If your own result looks wildly different, check that each figure is in the right unit and period (weekly, monthly or yearly) before drawing conclusions.