How much can you borrow for an investment property?
Investor lending is trickier than buying your own home. Lenders only count part of your rental income as safe — the rest, typically 75–85%, gets ignored. They also apply tighter debt-to-income limits and re-test your existing loans at higher stress rates. Of our 73 active lenders, 72 write investor loans — and they rarely agree on the number.
Looking for owner-occupier borrowing capacity instead? Use the standard borrowing capacity calculator →
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How we got this
Working out the math…
Why investor borrowing capacity is its own calculation
If you've already been through a borrowing capacity calculator as an owner-occupier, you'd be forgiven for thinking the investor version is just "same engine plus rental income added in." It isn't. Three things happen at the lender side that change the maths materially:
- Portfolio debt is stress-tested at the new lender's rate. Your existing investment loans don't count at the rate you're actually paying. Each lender re-amortises them at their own assessment rate (typically 8.5–9%) over the remaining term, regardless of whether you're sitting on an IO loan at 6.5% with a fixed-rate buffer. A $500,000 IO loan that costs you $2,700/month in real life shows up as $4,200/month of imputed servicing on the new file. Multiply across 2–3 IPs and the gap eats a meaningful chunk of borrowing capacity that an OO-only calculator wouldn't show you.
- Rental shading is the single biggest investor-specific spread driver. Lenders shade gross rental income to between 75% and 85% — call it the "vacancy and maintenance haircut" the lender takes off the headline rent before counting it as servicing income. NAB shades at 85%, most majors sit at 80%, conservative non-banks closer to 75%. On a $60,000 annual portfolio rent, that's a $6,000/year spread in assessable income — about $50,000 of borrowing capacity at typical DTI multiples. Different lender, different number, same property.
- Investor DTI is often tighter than owner-occupier DTI at the same lender. APRA's macroprudential focus on investor lending means most major lenders apply a tighter DTI ratio cap to investment loans than to owner-occupier loans — some at 6× vs 7×, others at 7× vs 8×. The calculator applies the right one per lender.
What this calculator does not yet model
- Negative gearing add-back. Some lenders (Westpac, CBA, NAB, ANZ traditionally) gross up rental income for the tax savings of a negatively-geared property — adding a few thousand back into assessable income. Smaller non-banks often don't. v1 doesn't apply per-lender add-back rules, which means the result is slightly conservative at lenders that do apply them. v2 will surface this per lender.
- Cross-collateralisation. If your portfolio loans are cross-collateralised, the structural question of whether to uncross before adding another property is a deal-stage conversation. The calculator's borrowing-capacity result is still meaningful — it tells you what each lender will service — but the "best lender for this deal" answer depends on whether you can split the structure cleanly.
- Depreciation schedules. Some lenders accept depreciation as an add-back to rental income; some treat it as a non-cash expense and ignore it. v1 doesn't model depreciation per lender — the user provides shaded rental income only.
- Trust and company structure surcharges. Borrowing through a discretionary trust or corporate structure changes the lender list (some won't write to trustees) and can change pricing. v1 treats borrower entity as PAYG/SE individual; the structure conversation belongs at deal stage.
- Investment loan history. Some lenders penalise borrowers who've shifted between investor lenders frequently or who have impaired investor lending history. v1 doesn't model this; we surface it on file.
What you should do with this number
The headline borrowable number is a panel-spread snapshot — useful for "is this purchase realistic against my current shape?" Not a deal-binding figure. The real value of the result is the lender-by-lender breakdown: which lenders give you the most room, why each one disqualifies (or doesn't), and how the gap between top-of-panel and big-4-floor changes when you add another property to the portfolio. That's the conversation we have when we sit down with your file — but you should walk in already knowing the panel shape rather than discovering it from the broker.
For the longer-form structural read — the three spreads (rental shading, 95% LVR cliff, negative-gearing add-back) that decide where an investor file actually goes — see the investor lending playbook.