Mortgage Calculator

Real monthly repayments, what LMI costs you, and what extra repayments are worth.

Your home loan
Per year
Per year
Monthly equivalent
Approximated annually — really a one-off premium.
Optional. See what overpaying does to the term.

How this is worked out

Repayments use the standard amortisation formula, applied monthly:

M = P · r(1+r)ⁿ ÷ ((1+r)ⁿ − 1)

where P is the amount borrowed, r is the annual rate divided by twelve, and n is the number of months. Early repayments are mostly interest, because interest accrues on the outstanding balance; as it falls, more of each identical repayment reduces the principal.

Council rates, insurance and strata levies are added monthly. LMI is really a one-off premium, normally capitalised into the loan; it is spread monthly here so the figures stay comparable, and the total is shown separately.

A worked example

Property price
$850,000
Deposit (20%)
$170,000
Loan amount
$680,000
Rate / term
6.1% over 30 years
Monthly repayment
$4,119.79
Council rates ($2,400/yr)
$200.00
Insurance ($1,800/yr)
$150.00
Total each month
$4,469.79

LMI is the cost of a small deposit, and it is larger than people expect

Lenders Mortgage Insurance is charged when you borrow more than eighty per cent of the property value. It insures the lender against your default. You pay it; you receive nothing for it.

The premium is not linear. At 85% loan-to-value it might be around one per cent of the loan; at 90% it roughly doubles; at 95% it can exceed four per cent. On a $680,000 loan that is a range from roughly $7,000 to over $27,000 — and because it is normally capitalised into the loan, you pay interest on it for thirty years.

This is why the gap between a 19% deposit and a 20% deposit is worth far more than one per cent of the purchase price. If you are close, finding the difference — or using a guarantor, or checking whether your profession qualifies for an LMI waiver, as many medical and legal roles do — is usually the single highest-value decision in the whole purchase.

Offset accounts change the arithmetic

An offset account is a transaction account linked to your loan, where every dollar sitting in it reduces the balance interest is calculated on. Twenty thousand dollars in offset against a $680,000 loan means you are charged interest on $660,000.

The effect is identical to overpaying, with one large advantage: the money remains yours and immediately accessible. At 6.1%, twenty thousand dollars in offset saves about $1,220 a year in interest — equivalent to a savings account paying 6.1% tax-free, which does not exist.

This calculator does not model an offset directly, but the extra repayment field is a good proxy: entering the interest a given offset balance would save shows you the same effect on the term. Offset accounts usually come with a higher rate or an annual fee, so the balance you keep in it needs to be large enough to justify that.

Principal and interest, or interest only

Interest-only loans keep repayments low by paying nothing off the principal — typically for one to five years. For an investor with a negative gearing strategy that can be deliberate. For an owner-occupier it usually means a much larger repayment later, on a shorter remaining term, plus more total interest.

APRA has restricted interest-only lending to owner-occupiers considerably, and lenders price it higher. If you are considering it to make a purchase affordable, that is a signal the purchase is not affordable rather than a solution to it.

This calculator models principal and interest only, which is what the large majority of owner-occupier loans are.

Stamp duty and the rest of the upfront cost

Stamp duty is a state tax and it is substantial — often twenty to forty thousand dollars on a median-priced home. Concessions and exemptions for first home buyers differ in every state and territory, and are worth researching properly rather than assuming.

Add conveyancing, building and pest inspections, loan application fees and lenders’ legal costs. Budget four to five per cent of the purchase price in cash on top of your deposit, and remember stamp duty cannot be borrowed.

Assumptions and sources

Amortisation formula
Standard annuity formula applied monthly. Verified in tools/test/finance.mjs against published repayment tables.
LMI thresholds
Charged above 80% loan-to-value; premium rises sharply with LVR. Waivers exist for some professions. checked 2026-08
LMI premium range
Approximately 1% of the loan at 85% LVR to over 4% at 95%. Varies by insurer — obtain a quote. checked 2026-08
Council rates and strata
You enter your own figures. Set by local council and by the owners corporation respectively.
Rates current as of 2026/27 — verify before relying on this. LMI premiums vary considerably between insurers and loan-to-value bands. Your lender will quote the actual figure.
Questions

What people ask about Australian home loans

How much is LMI?

It depends steeply on your loan-to-value ratio — roughly 1% of the loan at 85%, about double that at 90%, and over 4% at 95%. On a $680,000 loan that ranges from about $7,000 to more than $27,000, normally capitalised so you pay interest on it too.

How can I avoid paying LMI?

Have a deposit of 20% or more, use a guarantor, or check whether your profession qualifies for a waiver — many medical, legal and accounting roles do. If you are close to 20%, finding the difference is usually worth far more than it costs.

Does an offset account really help?

Yes, substantially. Every dollar in offset reduces the balance interest is charged on, with the money staying accessible. At 6.1%, $20,000 in offset saves roughly $1,220 a year — the equivalent of a tax-free 6.1% savings account.

Should I take interest-only repayments?

Rarely, as an owner-occupier. Repayments jump sharply afterwards on a shorter remaining term and you pay more interest overall. If interest-only is what makes a purchase affordable, the purchase probably is not.

Is stamp duty included in this?

No. Stamp duty is a separate state tax, often $20,000–$40,000 on a median home, and it cannot be borrowed. First home buyer concessions vary by state and are worth checking carefully.

Related

Next steps

Loan & Auto Loan Calculator Payment, total interest and a refinance comparison. Compound Interest Calculator Contributions, frequency and an inflation toggle. Take-Home Pay Calculator Gross to net, with the deductions your country actually applies. Credit Card Payoff Calculator The minimum-payment trap, avalanche versus snowball.