What this calculator does
The repayment quoted by a lender is only part of what a house costs each month. Property rates, building insurance and, for apartments, strata or HOA fees arrive on the same budget whether or not the loan covers them. This calculator puts all four in one figure, so the number you plan around is the number you actually pay.
It also reports the loan-to-value ratio, which is the fraction of the property’s price you are borrowing. That ratio drives whether lenders require mortgage insurance and which rate tier you qualify for, so it is worth watching as you adjust the deposit.
The formula
Principal and interest use the standard amortisation formula on the amount left after your deposit. Annual property tax and insurance are divided by twelve and added, along with any monthly strata or HOA fee, to give the total monthly outgoing.
| Term | Meaning |
|---|---|
| P | Loan amount: the property price less your deposit. |
| i | Monthly interest rate: annual rate ÷ 12 ÷ 100. |
| n | Number of monthly payments across the term. |
| LVR | Loan-to-value ratio: the loan as a percentage of the property price. |
The inputs explained
| Field | What to enter |
|---|---|
| Property price ($) | The agreed purchase price. Stamp duty and legal fees are paid separately and are not part of the loan here. |
| Deposit / down payment ($) | Cash you are contributing. A larger deposit lowers both the loan and the loan-to-value ratio. |
| Annual interest rate (%) | The annual interest rate on the loan. |
| Term (years) | The loan term in years: 25 and 30 are the most common. |
| Property tax / rates per year ($) | Council rates, land tax or property tax for a full year. |
| Insurance per year ($) | Building and contents insurance for a full year. |
| Strata / HOA per month ($) | Strata levies, body corporate fees or HOA dues, per month. Enter zero for a freestanding house. |
When to use it
Working out what you can actually afford
Lenders assess what they will lend; only you can assess what you can carry. Put in the full picture, rates, insurance, strata, and check the total against your after-tax income. A widely used guideline is keeping housing under about 30% of gross income, though that is a rule of thumb rather than a rule.
Testing a rate rise
Run your numbers at today’s rate, then again two or three percentage points higher. If the higher figure is unmanageable, the loan is larger than it looks, regardless of what the current repayment suggests.
House versus apartment
An apartment often has a lower price but carries strata fees that a house does not. Entering both properly is the only fair comparison: a $100 weekly strata levy is the equivalent of roughly $80,000 of extra borrowing at typical rates.
Deciding how much deposit to put in
Watch the loan-to-value ratio as you move the deposit. Crossing below 80% typically removes the requirement for lenders mortgage insurance, which can be worth more than the interest saved on the extra deposit itself.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
Monthly cost of an $800,000 home at different rates
A 20% deposit on an $800,000 property leaves a $640,000 loan. Only the interest rate changes between rows.
| Interest rate | Total monthly cost | Principal & interest | Total interest over term |
|---|---|---|---|
| 3% | $3,023.27 | $2,698.27 | $331,375.69 |
| 4% | $3,380.46 | $3,055.46 | $459,964.84 |
| 5% | $3,760.66 | $3,435.66 | $596,837.02 |
| 6% | $4,162.12 | $3,837.12 | $741,364.41 |
| 7% | $4,582.94 | $4,257.94 | $892,856.95 |
| 8% | $5,021.09 | $4,696.09 | $1,050,593.58 |
How the deposit changes the picture on a $700,000 home
Every dollar of deposit is a dollar not borrowed, and lowers the loan-to-value ratio at the same time.
| Deposit | Total monthly cost | Loan amount | Loan-to-value ratio | Total interest over term |
|---|---|---|---|---|
| $35,000 | $4,287.01 | $665,000.00 | 95.0% | $770,323.96 |
| $70,000 | $4,077.17 | $630,000.00 | 90.0% | $729,780.59 |
| $105,000 | $3,867.33 | $595,000.00 | 85.0% | $689,237.22 |
| $140,000 | $3,657.48 | $560,000.00 | 80.0% | $648,693.86 |
| $210,000 | $3,237.80 | $490,000.00 | 70.0% | $567,607.13 |
What price can a budget carry at 6%?
Holding the rate and term steady and moving the price shows how the monthly figure scales.
| Property price | Total monthly cost | Loan amount | Loan-to-value ratio |
|---|---|---|---|
| $400,000 | $2,081.98 | $300,000.00 | 75.0% |
| $600,000 | $3,281.09 | $500,000.00 | 83.3% |
| $800,000 | $4,480.19 | $700,000.00 | 87.5% |
| $1,000,000 | $5,679.29 | $900,000.00 | 90.0% |
| $1,200,000 | $6,878.39 | $1,100,000.00 | 91.7% |
Questions
Does this include stamp duty or closing costs?
No. Those are one-off costs paid at settlement, not monthly ones, and they vary widely by location. Budget for them separately alongside your deposit.
What is lenders mortgage insurance and is it included?
It is a premium charged when you borrow above about 80% of the property value; it protects the lender, not you. It is not included here. If it applies, it is usually added to the loan balance, so you can approximate it by increasing the loan amount.
Should I use the interest rate or the comparison rate?
Use the plain interest rate to reproduce a lender’s quoted repayment. Use the comparison rate if you want a figure that reflects fees as well, though the result will then be an estimate rather than the exact instalment.
Why is my loan-to-value ratio important?
It determines both whether mortgage insurance applies and, often, which rate tier you are offered. Lenders price risk, and a smaller loan against the same asset is a lower risk.
How much should property rates and insurance be?
Both vary enormously by location and property type. The starting values here are placeholders: check the actual rates notice and an insurance quote for the specific property, since a wrong figure here shifts the total meaningfully.
For a plain loan without property costs, use the loan payment calculator. To see the maximum loan a repayment supports, try how much can I borrow, and check serviceability with the debt-to-income calculator.