NZ Borrowing Capacity Calculator — RBNZ DTI-Aware (2026)

New Zealand's borrowing capacity calculation is now governed by RBNZ's Debt-to-Income caps, introduced July 2024 — the first jurisdiction in this region to apply explicit DTI ceilings. This calculator applies the 6× (owner-occupier) and 7× (investor) caps alongside lender servicing tests to give you a realistic borrowing ceiling.

What changed in July 2024

The Reserve Bank of New Zealand introduced DTI restrictions as a macroprudential tool — a way to slow credit growth in residential property without changing the OCR. Two key numbers:

• Owner-occupiers: 6× gross income
• Investors: 7× gross income

These are caps on the loan size relative to gross household income. A household earning $180,000 can borrow up to $1.08m as owner-occupier or $1.26m as investor, before any other restriction.

There's a 20% allowance — lenders can write up to 20% of new owner-occupier loans above the 6× cap, and 20% of new investor loans above the 7× cap. So individual approvals above the cap are possible but limited. From the borrower's perspective, the cap is effectively binding most of the time at most lenders.

DTI cap vs lender servicing

DTI is one of two binding constraints. The other is servicing — the lender's own assessment of whether you can afford the repayments at a stress-tested rate.

DTI is a hard regulatory ceiling on loan size relative to gross income.

Servicing is calculated by the lender at an assessment rate (typically contract rate + 2–3% buffer) and tests whether your post-tax disposable income covers the assessed repayment plus living expenses plus other debts.

For most borrowers, servicing is tighter — your post-tax disposable income usually constrains you below the DTI ceiling. The DTI cap binds for high-income, low-debt borrowers buying expensive properties.

The calculator surfaces both numbers so you can see which one binds for your specific scenario.

What lenders include in the DTI calculation

Income side:

• PAYE salary (gross)
• Self-employed taxable income (averaged 2 years)
• Investment income (rental, dividends, interest)
• Government benefits (some, with shading)

Debt side (counted toward the cap):

• Existing mortgages (full amount)
• Personal loans (full amount)
• Car loans (full amount)
• Credit card limits (full limits, not balances — even unused capacity counts)
• HELOC / revolving credit (full limits)
• Other line-of-credit facilities

The credit card limits trap is the biggest one most borrowers don't see coming. A $20,000 credit card with a $0 balance still counts as $20,000 of debt for DTI purposes. Closing unused cards before applying for a mortgage often unlocks meaningful additional capacity.

How to maximise your NZ borrowing capacity

In rough order of impact:

1. Close unused credit card and revolving credit limits. Single biggest free lever. A $30,000 in unused limits is $30,000 of borrowing capacity you've given up.
2. Pay down personal loans and car loans before applying. Even if cashflow-equivalent, lowering the debt balance directly increases borrowing capacity.
3. Add a co-borrower if possible. Two income earners on the loan combines income for the DTI numerator.
4. Reduce living expense baseline. Cancel subscriptions, downgrade insurance, reduce discretionary expenses for 3 months before applying — the bank looks at your actual statements.
5. Time your application around income changes. Bonuses, commission, a recent pay rise — get the highest-income payslips you can show.
6. Shop multiple lenders. Some lenders are within their high-DTI allowance bucket on a given month; others have used theirs. Brokers who know which is which can find capacity that one bank alone can't write.

Owner-occupier vs investor — different caps, different LVR

Owner-occupier:

• DTI cap: 6× gross income
• Standard LVR: ≥20% deposit (≥80% LVR)
• High-LVR allowance: banks can write up to 15% of OO loans above 80% LVR

Investor:

• DTI cap: 7× gross income (higher, reflecting rental income servicing)
• Standard LVR: ≥30% deposit (≥70% LVR)
• High-LVR allowance: tighter than for OO

The investor DTI is higher because the rental income from the investment property is added to the income side; the higher LVR requirement reflects the higher default risk on investment properties.

What the calculator does

1. Calculates your maximum borrowing under the RBNZ DTI cap
2. Calculates your maximum borrowing under lender servicing at the assessment rate
3. Returns the lower of the two as your effective borrowing capacity
4. Shows which constraint binds, so you know which lever to pull to increase capacity

For pre-approval purposes, the binding constraint at any given lender is often servicing rather than DTI — but the DTI cap is the hard regulatory ceiling, and getting your DTI down is the cleanest path to higher capacity at any lender you might switch to.