Property Development Feasibility Calculator Australia

What this property development calculator does

A property development only works if the end values cover the land, the build, the interest and the risk, with enough left to justify doing it at all. This calculator sets that test out in the standard feasibility form: gross realisation at the top, GST and selling costs deducted to give net realisation, then the full cost stack, and the profit as a margin on cost and a margin on realisation.

It is built for a small residential project, a duplex, a townhouse site, a handful of units, and it answers the two questions a developer asks before making an offer: does this stack up at the asking price, and what would I have to pay for the land to make it stack up?

Building up the revenue side

Gross realisation is the number of dwellings multiplied by the expected sale price. It is the input the whole feasibility is most sensitive to and the one most often set by hope rather than evidence. Use recent settled comparables of the same product in the same street, not asking prices, and not the price the selling agent needs to win the listing.

Two things come off before the money is yours. Selling costs, including agent commission, marketing and legals, take a percentage of the gross. GST takes more, and how much depends on the treatment.

Under the margin scheme, GST is one eleventh of the margin between the sale price and what you paid for the land. Under the ordinary rules it is one eleventh of the whole sale price. On a site bought for 1.15 million and selling for 4.6 million, the margin scheme costs about 314,000 dollars of GST against roughly 418,000 under the full treatment, so the difference is real profit. The scheme is not automatic: it must be agreed in writing before settlement and the land must have been acquired in a way that permits it, so confirm eligibility with your adviser before relying on it in a feasibility. The third option, input taxed, applies where the sale is not a taxable supply, most commonly existing residential premises that have merely been renovated rather than substantially reconstructed.

Building up the cost side

Land is the starting point, plus acquisition costs such as transfer duty, conveyancing and due diligence. Duty varies by state and by the value of the site, so it is entered as a figure rather than calculated here; the stamp duty tool will give you the number for your state.

Construction is entered as a rate per square metre against the total build area. There is no published national rate, and the honest answer is that it depends on the product, the site, the state and the year, so this is your figure to source from a builder or a quantity surveyor. Professional fees, including the architect, engineers, town planner, surveyor, certifier and project management, are taken as a percentage of construction. Council contributions and authority headworks charges are entered separately because they vary so much between councils that no percentage would be meaningful.

Contingency sits on top of construction and fees. Five per cent is a common starting point on a straightforward build and light on anything with an existing structure, difficult ground or a long approval history.

Holding costs cover rates, land tax, insurance and site security across the project term. Finance is charged on the debt-funded share of costs: a full term of interest on the land debt, which is drawn at settlement, and interest on roughly half the works facility, which is drawn progressively. Peak debt is reported separately, since that is the exposure a lender sizes against.

Reading the result

The headline is the development profit and the margin on cost beside it. Most lenders and most developers want 18 to 25 per cent on cost for a small residential project; the margin is compensation for risk, and a thin one disappears the moment a trade prices higher or the market softens between approval and completion.

Two derived figures matter as much as the profit itself.

Residual land value solves the feasibility backwards. Holding the end values, the build cost and your target margin fixed, it returns the land price that would exactly hit that margin. Compare it against the asking price: if the residual is well below, the site is either overpriced or needs a different scheme, and no amount of optimism in the sale prices will fix it honestly.

Break-even sale price per dwelling is the other side of the same question. It is the price at which the profit is zero, and the gap between it and your expected sale price is your real buffer against a falling market. If break-even is 975,000 dollars and you are relying on 1,150,000, you have about 15 per cent of headroom.

What the model leaves to you

The feasibility is a static one: it does not run a cash flow month by month, so it will not show you when the peak funding requirement falls or how a delayed approval changes the interest bill. Nothing is discounted to present value; profit is nominal, not an internal rate of return.

Income tax and, where relevant, the tax treatment of the profit in your structure are outside the model. So is any pre-sale or staged settlement arrangement, and so are the escalation clauses in a building contract. Every figure is entered by you except the GST rate, which is stored as an ATO parameter and updates automatically.

Sensible ways to use it

Run the site as offered first, then change one variable at a time. Drop the sale price by five per cent and see what happens to the margin; that single test kills more sites than any other. Add three months to the program and watch the finance and holding costs move. Lift the construction rate by ten per cent, because it is the input most likely to be wrong on the low side.

Then work backwards. Set your target margin, read the residual land value, and let that number, rather than the asking price, be the basis of your offer.

This is a screening estimate built entirely on your own assumptions, not a valuation or a funding submission. Have any site you intend to buy assessed by a quantity surveyor, a valuer and a tax adviser before you commit, and confirm the GST treatment in writing before settlement.

This is general information only and not financial advice.

About This Tool: Property Development

Property development: use this tool to get an instant, accurate estimate. The figures follow official ATO guidance and every rate and threshold is kept up to date for 2026. Adjust the inputs above to match your situation, or browse all our calculators to plan your next step.