Home loan calculators, explained
Calculators are useful for getting oriented, as long as you know the assumptions built into each one. Below is what each common home loan calculator does and what to watch for. Our one interactive tool, the budget planner, runs entirely in your browser with no data capture.
Last updated July 2026Budget planner
What it does. Totals income against living costs to show your monthly surplus and savings rate.
Watch for. Only as accurate as the numbers you enter. Round expenses up, not down.
Open the budget planner →Repayment calculator
What it does. Estimates the regular repayment on a loan from the amount, interest rate and term.
Watch for. Assumes a fixed rate for the whole term. Real rates and fees change the figure.
Borrowing power
What it does. Estimates how much you might borrow from income, expenses and existing debts.
Watch for. A guide only. Lenders apply a serviceability buffer and their own policy, so results differ.
Offset savings
What it does. Shows how a balance in an offset account reduces the interest charged on the loan.
Watch for. Benefit depends on keeping a real balance. A near empty offset saves little.
Comparison rate
What it does. Combines the interest rate with most standard fees into a single percentage.
Watch for. Based on a standard example loan, so it may not match your amount or term.
Stamp duty
What it does. Estimates transfer duty on a purchase, which varies by state and buyer type.
Watch for. Rules and concessions change. Confirm with the relevant state revenue office.
Why every result is an estimate
A calculator can only work with the assumptions coded into it. It does not know your full financial position, the exact fees on a product, or how a lender will apply its policy. That is why a repayment or borrowing figure from any calculator, including ones on lender websites, is a guide rather than a promise.
Under guidance from the prudential regulator, lenders assess your ability to repay at an interest rate around three percentage points above the actual rate. That serviceability buffer is one big reason a simple online borrowing figure can differ from what a lender ultimately approves.
Use calculators to explore and compare, then confirm anything important with a lender or a licensed credit adviser before you rely on it.
Start with the numbers you control
The most useful place to begin is your own cash flow. Knowing your monthly surplus tells you far more than a headline borrowing figure, because it is grounded in what you actually earn and spend. Open the budget planner to map it out.
Understand the tool, then use it
Read how each calculator works, then run your real figures through the budget planner.
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This is an educational estimate, not a loan approval, quote or advice. It ignores tax, fees, lender policy and your full circumstances, and nothing you enter is sent anywhere or stored. Actual borrowing capacity and repayments are set by a lender after assessment. Speak with a licensed Australian credit adviser before making decisions.