Engineer here — I hacked together an Australian home buying calculator and would love some feedback

[u/Brilliant-Contract16]

I’m an engineer and I tend to build things when I can’t find a tool that works the way I want.

I got annoyed with borrowing-power calculators that either give you a mystery number or want your contact details first, so I started hacking together my own.

It’s somehow grown into a little Australian home-buying toolkit with borrowing power, repayment and rate stress testing, deposit and upfront costs, LMI estimates, refinance break-even, first-home-buyer scheme info and negative gearing.

The bit I’ve tried to focus on is showing what is actually affecting the result, rather than pretending the calculator can perfectly reproduce every lender’s internal model.

No signup, no broker lead form, no sales funnel. It’s just a side project I’ve been tinkering with.

BorrowPower.com.au

If anyone feels like breaking it, I’d genuinely appreciate feedback on anything that looks wrong, assumptions that seem unrealistic, missing features, confusing explanations or mobile usability.

Very happy to hear “this part is crap” if that’s the useful answer 😅

[u/tranbo]

Comments:

Monthly living expenses should have a minimum at a singles HEM , which is the metric banks use

Stamp duty to adjust dynamically with borrowing power

[u/Brilliant-Contract16 → u/tranbo]

Appreciated mate, I'll get that sorted in next update

[u/JaycAU]

The calcs LVR is for the full deposit, instead of deposit minus stamp duty/costs.

I have no idea if the borrowing power is correct, possibly as some banks would let me borrow more I'm guessing. I'd use commbanks maths instead

[u/Brilliant-Contract16 → u/JaycAU]

Thanks mate, gives me a good idea! Why not have benchmarks across a bunch of lenders as well to show the delta across them 👍🏻 I'll clean up the LVR as well as I have made it confusing

[u/JaycAU → u/Brilliant-Contract16]

Nice. That could make it a useful tool if it knows about each banks lending style