Borrowing Power Calculator Australia 2026 - APRA Rules Explained

The APRA 3% Serviceability Buffer - Australia's Most Misunderstood Mortgage Rule

Many buyers focus on the headline rate on the lender's website. Banks do not. APRA says the mortgage serviceability buffer remains at 3 percentage points, and its earlier guidance explains that the buffer was lifted from 2.5 to 3.0 percentage points in October 2021. So if your offered rate is 6.50%, the lender will usually assess whether you could still repay at about 9.50%, not 6.50%. That is why Australian borrowing power can look materially lower than overseas calculators suggest.

2026 Update - The New DTI Cap Sits Alongside the Buffer

From 1 February 2026, APRA also activated debt-to-income limits. For ADIs, no more than 20% of new owner-occupied lending and 20% of new investor lending can be written at a DTI ratio of six or more, measured separately. APRA has also said the cap is not currently binding at a system level, so it is better understood as a guardrail than a blanket ban. Still, if your borrowing relies on stretching to six times income or more, this is now part of the 2026 lending landscape.

HECS/HELP Debt - The Australian Factor Most Calculators Miss

HELP debt matters because the repayment is not theoretical. The ATO says the minimum repayment income for 2025–26 is $67,000, and compulsory repayments moved to a marginal repayment system from that income year. In practice, that means borrowers with HELP debt can have thousands of dollars a year diverted from cash flow once their income is high enough. Because lenders assess borrowing power from income after accounting for debts, liabilities and living costs, HELP can materially reduce the amount you can borrow even when your salary looks strong on paper.

Other Australian Factors That Affect Borrowing Power

Borrowing power is not just salary multiplied by a bank ratio. Lenders look at your income, existing debts, regular expenses and household profile. NAB's consumer guidance says borrowing power is influenced by net income, existing debts, regular expenses, number of dependants, interest rates and loan type. Moneysmart similarly notes that lenders look at income, debts and everyday expenses when working out whether you can afford repayments.

Rental income is another area where assumptions matter. There is no single universal rental-income rule across every lender. NAB has disclosed that it applies 10% shading to rental income and also includes rental expenses in serviceability. That is why a conservative calculator should never assume every dollar of gross rent is fully available for borrowing power. This estimate uses lender-style shading and stays pre-tax rather than baking in assumed negative-gearing benefits.

Dependants matter as well. Australian lenders generally assume a household with children or other dependants has higher living costs, which reduces the monthly surplus available for repayments. That does not automatically mean a loan will be declined, but it usually means a lower borrowing-capacity ceiling than a similar household without dependants.

Why Your Estimate May Be Lower Than Expected

The usual culprits are not mysterious. It is often the APRA buffer, HELP repayments, credit-card limits, dependants and higher declared living costs. Even applicants with solid incomes can see their estimate fall once the bank applies real-world serviceability settings instead of optimistic online assumptions. That is especially true in 2026 for borrowers already pushing toward high-DTI territory.