Borrowing Power Mistakes Australians Make and How to Avoid Them

Updated 11 July 2026 · Property and home loans

A Borrowing Power 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 borrowing power calculations in Australia, and how to avoid them.

1. Assuming prices always rise

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

2. Borrowing the maximum

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

3. Forgetting purchase costs

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

4. Comparing headline rates only

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

5. Overlooking the detail that matters most here

Lenders count credit card limits, not balances. Closing unused cards can raise your borrowing power.

How the estimated borrowing power changes with monthly living expenses

A common mistake is getting one input slightly wrong. Here is what happens to the estimated borrowing power when “Monthly living expenses ($)” is off by up to 20% in either direction, with everything else held steady.

Monthly living expenses ($)	Estimated borrowing power
2,800	$512,908.39
3,200	$464,071.60
3,500	$427,444.01
3,900	$378,607.22
4,200	$341,979.63

At 2,800 the result is $512,908.39; at 4,200 it is $341,979.63. 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

Surplus = after-tax monthly income − expenses − debts. Borrowing power = the loan that surplus repays at your rate plus the 3% APRA buffer. With typical inputs the calculator returns estimated borrowing power of $427,444.01. 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.