What changes house extension costs
The shell, tie-in to the existing home, engineering, approvals and wet-area fitout must be allowed for separately.
Updated August 2026
House Extension Cost Calculator Australia
Estimate house extension costs anywhere in Australia using postcode-aware pricing and project-specific decisions.
✓ Australian postcode pricing✓ Detailed project inputs✓ Free personalised PDF✓ Editable source rates
Aurenoo Australian cost planner
House Extension cost calculator
Build a postcode-adjusted low, central and high planning range using options relevant to your project.
1 Location2 Project3 Details4 Estimate
Decision comparison
House Extension costs by finish level
Default scenario: 40 m². Use the calculator for your actual project.
FinishLowCentralHigh
BasicAUD 76,500AUD 108,000AUD 150,000
StandardAUD 93,000AUD 131,000AUD 183,000
PremiumAUD 126,000AUD 177,000AUD 246,000
LuxuryAUD 154,000AUD 217,000AUD 301,000
Scope and decision checklist
Compare the same project across cities and finish levels before selecting a working budget.
Budget planning guidance
The free detailed PDF records your pricing inputs, breakdown, assumptions and next-step checklist.
Before you set the budget
Three decisions that protect your renovation budget
Define the same scope
Write down demolition, retained items, service moves, finishes, approvals and exclusions so every comparison covers the same work.
Separate allowances from fixed prices
Track provisional sums and prime-cost items separately. These are common sources of budget movement after work starts.
Hold a risk reserve
Keep the difference between the central and high estimate visible until access, structure and concealed conditions are confirmed.
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Local comparison
Compare this project across Australian cities
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Planning approach
How to use this estimate
Choose location
Use an Australian postcode, suburb or listed city.
Define the project
Enter size, finish and only the decisions relevant to the selected category.
Compare the range
Use the central result for planning and retain the high range until risks are checked.
Download details
Keep the free report with assumptions, allowances and your quote checklist.
Important: this is a feasibility tool, not a contractor quote. Validate selections, approvals, existing conditions and access before committing funds.