Construction cost estimator/calculator
New homes, renovations & extensions

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Caveat lector! (Reader beware!)

Our construction cost calculator only gives an estimate of building costs. It is only suitable for use before any detailed plans are made. Note: You will need to adjust the default per-square-metre cost to a value more suitable for your area.

For accurate construction costs you will require detailed construction plans and the services of a quantity surveyor or licensed builder.

Also note: The cost of renovations are often impossible to estimate due to unseen structural issues in the building. However the cost of extensions can usually be determined as accurately as the cost of a new home.

If you speak to a few builders in your area you should be able to get reasonable per-square-metre costs for your own location and requirements. The assumptions shown below are based on the author's personal experience building custom homes in NSW - they do not apply to kit homes or project homes, which are much cheaper to build (and currently cost approximately $900 - $1200 per square metre).

Cost assumptions

Cost assumptions built into by our construction cost calculator are as follows (but you can easily change them):

• A custom designed house on an excellent site using basic finishes will cost $1500/square-metre.
• A custom designed house on an excellent site using standard finishes will cost $1700/square-metre.
• A custom designed house on an excellent site using luxury finishes will cost at least $1900/square-metre.
• If the site is "good", but not excellent, add 7% to the cost.
• If the site is "difficult", add at least 20% to the cost.
• Renovations cost twice as much, per square metre, as new home construction or extensions.

Where to find costing data

• Building Express Calculator: Use this calculator (created by Reed Construction Data) in combination with ours for comparison purposes, or to get a per-square-metre cost for your own area (that you can then use in our construction cost calculator).
• BMT & Assoc Quantity Surveyors: Construction costs per-square-metre for the Sydney region.

Start calculating your construction costs >>

Further reading

You may find it beneficial to read the following related home design and building articles: