About this calculator
Australian home loans have three moving parts that a generic mortgage calculator misses. First, the offset account: money sitting in a linked transaction account is subtracted from your loan balance before interest is calculated, so your repayment stays the same but the loan melts faster. Second, lenders mortgage insurance (LMI): with a deposit under 20% you pay a one-off premium — usually added to the loan — that protects the lender, not you. Third, stamp duty: there is no national rate. Each state and territory sets its own banded table (the NT uses a formula), and first-home-buyer concessions differ just as much.
Pick your state above and this calculator applies that state's duty table and first-home rules — all eight jurisdictions are covered, including Queensland's and South Australia's duty-free new builds for first home buyers and the ACT's nil duty for eligible home buyers. For the full picture there are dedicated tools below: borrowing power tested at APRA’s buffered rate, a banded LMI estimator, an offset deep-dive, and a first-home-buyer calculator that adds the FHOG or HomeGrown grant to the duty picture.
How to use it
- Enter the property price and your deposit — the difference, plus any LMI, is the loan amount.
- Add the interest rate and loan term (30 years is the Australian standard).
- If you will keep savings in an offset account, enter the average balance — you will see the interest it saves and how much sooner the loan ends.
- Tick "first home buyer" if it applies: the stamp duty below then uses your state's first-home concessions.
- Read the monthly repayment, the stamp duty and the real payoff time with your offset.
The formula
M is the monthly repayment, P the loan amount, r the monthly rate and n the number of payments. An offset account does not change the repayment; it reduces the balance on which interest is charged, so more of each repayment becomes principal and the loan ends sooner. Stamp duty is charged by the state on the purchase price using that state's banded table.
Worked example
An $800,000 home in Sydney with a $160,000 deposit (20%) leaves a $640,000 loan with no LMI. At 6.00% over 30 years the repayment is $3,837 a month. NSW stamp duty on $800,000 is $30,187 — but a first home buyer pays none, because the NSW exemption runs to $800,000. Keep an average of $50,000 in an offset account and the same loan is gone in 25 years 7 months, saving about $204,666 in interest.
Sources: State revenue office duty schedules for 2026; LMI estimated from typical insurer premium curves. Last updated: October 2026.
Frequently asked questions
How does an offset account save interest?
Interest is charged on your loan balance minus your offset balance. With a $640,000 loan and $50,000 in offset, you pay interest as if you owed $590,000 — but your repayment is unchanged, so the extra goes straight to principal. Kept for the whole loan, $50,000 in offset saves roughly $204,666 of interest on that loan and clears it about 4½ years early. A redraw facility is not the same thing: offset money stays in your own account, instantly accessible.
What is LMI and when do I pay it?
Lenders mortgage insurance is a one-off premium charged when your deposit is under 20% (LVR above 80%). It protects the lender if you default — it does not protect you. Premiums rise steeply with LVR: roughly 1.5% of the loan at 85% LVR, 3% at 90% and 4.5% at 95% is a mid-range estimate, though insurers vary by ±50%. The premium is usually capitalised — added to your loan — which is how this calculator treats it.
How much is stamp duty on an $800,000 home?
It depends entirely on the state: about $30,187 in NSW, $43,070 in Victoria at general rates (owner-occupier concessions can reduce it below $550,000), $21,850 in Queensland at home-concession rates, $32,316 in WA, $37,830 in South Australia, $31,185 in Tasmania, $22,158 in the ACT on the owner-occupier schedule, and $39,600 in the NT. First home buyers pay far less or nothing in most states — NSW exempts homes to $800,000, the ACT charges eligible buyers nothing at any price — but Tasmania and the NT currently offer no first-home duty relief. Rates shown are the state tables current in October 2026.
Do first home buyers get the First Home Owner Grant too?
The grant (FHOG) is a separate cash payment for new homes, with its own caps and rules, so it is not deducted here — the dedicated first home buyer calculator on this site adds it in. Amounts run from $10,000 (NSW, VIC, WA) to $30,000 in Queensland and $50,000 under the NT’s HomeGrown grant; the ACT pays no grant because its duty concession does the work instead.
What formula does this home loan calculator — australia calculator use?
M = P × r(1 + r)^n ÷ ((1 + r)^n − 1), interest charged on (balance − offset) M is the monthly repayment, P the loan amount, r the monthly rate and n the number of payments. An offset account does not change the repayment; it reduces the balance on which interest is charged, so more of each repayment becomes principal and the loan ends sooner. Stamp duty is charged by the state on the purchase price using that state's banded table. The worked example on this page applies the formula step by step with real numbers, so you can verify the result by hand.