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Construction cost calculator

Aspect Designs, Sydney, NSW

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Gecko Homes

Central Coast Builder. New homes & renovations.

How it works

For a detailed explanation of how this residential construction cost calculator works read this article: 'Estimating building costs'.

If you already have detailed construction plans we recommend you get accurate quotes from local builders.

Step 1: Initialise the calculator

Select project type

Project definitions

  1. New house: A completely new dwelling.
  2. Renovation: Fixing up an existing house. Can include additions.
  3. Addition/Extension: Adding new spaces to an existing house. Requires roof extensions and wall removals.
  4. Separate pavilion: The creation of a separate building that may or may not be joined to the existing house with a covered walkway or something similar; e.g. a granny flat.

Step 2: Select site condition



  1. Excellent: Flat level block of land with no drainage issues.
  2. Good: Slightly sloping block. Minor drainage issues.
  3. Difficult: Steep block. Block with drainage issues. Bushfire zone.

Step 3: Quality of finishes



  1. Basic: By selecting this option you are stating that you will be buying items such as bathroom & kitchen fittings, door hardware, et cetera, where cost is of higher concern than quality or style.
  2. Standard: Selecting 'standard' states that quality is as important as cost, but style is less important than either.
  3. Luxury: Quality and style are more important than price.

Step 4: Per-square-metre costs

Based on the choices you made above we have set some average per-square-metre costs for you below. For more accurate values refer to BMT's construction cost table or contact a few local builders or residential architects.

Internal spaces:

per m2

Decks, verandahs & patios:

per m2


per m2

Step 5: Enter size of the following spaces

If you selected 'new house' the values below have been pre-set for a small 3 bedroom, open plan house.

Change the areas shown below to suit your requirements.



master bedroom


main bathroom


ensuite bathroom


2nd toilet/bathroom


walk-in robe


lounge area


bedroom 2




bedroom 3


rumpus area


bedroom 4


dining area






decks, patios & verandahs


indoor circulation


e.g. hallways, stairs, entrance

Other bedrooms X m2
Other bathrooms X m2
Other indoor areas X m2

Step 6: Get an approximate cost

Click this button to calculate/update the estimate below.

Total estimated cost:     $

Step 7: Get 3 quotes for an accurate cost

Don't waste time doing the ring around - get 3 local building professionals to give you a quote. It's obligation-free.

Your postcode

Frequently asked questions (FAQ)

Q. How accurate is your calculator?

A. Our calculator gives reasonable initial estimates, ie. before there are detailed plans. Experienced builders who use our calculator have told us they can get to within 10% of the final cost - so the better your research for reasonable per-square-metre costs, the more accurate our calculator will be. For reasonable per-square-metre costs in Australia use BMT's construction cost table. If you have not already done so read our article about Building Cost Estimates for more information.

Q. Where can I get cost data?

A. For reasonable per-square-metre costs for your local area refer to BMT's construction cost table or contact a few local builders or residential architects.

Q. Per-square-metre why do renovations, extensions & additions cost more?

A. There is a large difference between the per-square-metre cost of a new house and the per-square-metre cost of a renovation, extension or addition because there are usually unforeseen structural issues; e.g. plumbing & electrical problems, termite damage, etc. In addition there can be site-access issues, especially if the owners are still living in the house.

Q. What is circulation?

A. Circulation refers to hallways, entrances and stairways. Use 10% for a basic no-frills house. Use 20% - 25% if you want your house to feel spacious.

Q. How will my non-standard features such as high ceilings affect the cost?

A. Hard to say. The best you can do before detailed house plans are drawn up is increase the per-square-metre rates used by the calculator. The calculator has an option called 'Quality of finish' which allows you to select 'basic', 'standard' or 'luxury'. Selecting standard increases the per-square-metre rate by $300. Selection 'luxury' increases the rate by $600.

Video: How to keep construction costs down

Six essential tips you need to know. Read the article.


Coastal Construction & Building If you are building a new home or renovating on Sydney's North Shore, the Central Coast or the Hunter region, Coastal Construction & Building offer full-contract, project management or labour-only contracts so you can choose which contract option works best for you.
Aspect Design Aspect Designs are a multi-disciplined, award winning, Sydney based business who specialise in architecture, interior design, drafting and landscape design.
Angela Elliss Design Angela and her team understand that communication is the key to making your new home design or renovation a success. They are with you every step of the way, answering every question. Angela has over 15 years of experience in residential building design combined with an architecture degree from the University of Newcastle, NSW. If you are starting from scratch, renovating, or just need advice on where to start and how the building process works, give Angela a call. For detailed information visit the website.
Gecko Homes Gecko Homes specialise in new homes and renovations. Gecko Homes service the NSW Central Coast, Sydney and Newcastle.