Why do online mortgage calculators give a higher borrowing amount?

They only use the few numbers you type in. Banks also look at credit card limits, HECS, other debts, how your income is made up, your real spending and a rate buffer, which usually brings the figure down.

Why does every bank's calculator give a different answer?

Each bank has its own policy on income, living expenses and debts. The same person can get a noticeably different borrowing figure from one bank to the next.

Do credit card limits affect how much I can borrow?

Yes, even if the card has nothing owing. A rough rule of thumb is to times every thousand dollars of limit by five to see roughly how much it reduces your borrowing capacity.

What is the serviceability buffer?

Banks test whether you could afford the repayments at a rate higher than the one you'll pay, commonly around 3% above. It's one reason the bank's number is lower than many calculators.

How do I find out what a bank will actually lend me?

Have your real figures run through the banks' own calculators against their policy. A broker can do that across several lenders at once, then the final answer comes with the bank's approval.

Home / Straight Answers / Calculators vs the bank

Straight Answers · First home

Why do online calculators say I can borrow more than the banks will actually lend me?

Bayley Clarke · Mortgage broker on the road · Last checked 11 November 2026 · 3 min read

The short answer

Mostly because the calculator doesn't know what your actual financial situation looks like. It takes a handful of numbers you type in and spits out a figure, while the bank reads your whole financial world against its own policy. And every bank's online calculator gives a different result anyway.

Part of the work I do is sitting down with you and flipping over every stone, then running your real numbers through the banks' own calculators. That way the figure we talk about is based on how each bank will actually read your income, your spending and your debts, not a guess.

The 90 second version, filmed from the driver's seat. The rest of this page is the detail underneath it.

What the online calculator doesn't see

A public calculator asks for your income, maybe your partner's, a rough idea of expenses and whether you have kids. That's it. What it doesn't know is the stuff that actually moves the number. Your credit card limits, even if you never use them; to give you a bit of an idea, for every thousand dollars of limit, times it by five and that's roughly how much it hits your borrowing capacity. Your HECS. Your car loan. Your buy now pay later accounts. Whether your income is base salary or a chunk of it is overtime, bonus or casual, which banks treat differently.

The bank also doesn't assess you at the rate you'll actually pay. It adds a buffer, commonly around 3% on top, to make sure you could still afford the repayments if rates went up. Some online calculators don't show that clearly, so the figure looks bigger than any bank would approve.

Why every bank's number is different

Each bank writes its own policy and runs its own calculator. One counts all of your overtime, another counts part of it. One uses a higher living expense figure for your household size, another uses your declared spending if it's higher. One treats your HECS more harshly than the next. So the same person can get a noticeably different borrowing figure from bank to bank, with nothing about their situation changing.

That's why playing around with online calculators can set you up for disappointment. You land on the highest number you saw, start looking at properties at that price, and then find out the bank you applied with reads you very differently.

How I work out the real number

I go through your financial world properly: payslips, statements, debts, limits, what you actually spend. Then I plug that into the banks' own calculators, because I know how to translate your situation into the way each bank is going to read it. I check policy as I go, whether they're likely to approve you, and exactly which parts of your income and spending they will and won't use, and how much of each.

What you get at the end is a borrowing figure grounded in real bank policy, and usually a sense of which lenders stretch furthest for someone like you. I sift through the noise, and I get to charge the bank for the work at the end of it, not you.

The honest bit: a calculator figure isn't an approval, and neither is mine

Even a properly worked number still depends on the bank's credit check, the valuation on the property and the documents lining up. It's a far better starting point than an online estimate, but it's a starting point.

If you keep running calculators and the number is less, or more, than you expected, that's the moment to have a chat. Ten minutes of real numbers beats an afternoon of guessing.

Want a borrowing figure based on how the banks will read you?

A 30 minute call. We go through your income, debts and spending, and I run it through the banks' own calculators so you know your real range before you look.

Book a 30 minute call Call 0437 189 939

No cost to you. The bank pays me when a loan settles. · How I get paid

Next question

How much can I actually borrow?

Income versus outgoings, then the bank adds a buffer to your rate before it names a number.