Extension cost calculator: how much does it cost to extend your home in 2018?

Use our free extension cost calculator to help you work out a budget for the likely costs of your home improvement project

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The first step in any project should be establishing what you can afford to do, and this is especially important if you are undertaking a large job like extending your home. This free tool will estimate how much it is likely to cost to build an extension

Answer a few simple questions, including where you live, the kind of extension you’d like to add, and how much of the work you’d like to do yourself, and it will provide you with an instant, accurate result telling you how much your finished project should cost.

How much does a home extension cost?

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There are many factors involved in costing an extension project, from the size of the project right down to the quality of the paint you use on the walls. For a basic breakdown of average extension prices, follow these guidelines:

  • Approach several builders and get full quotes for the proposed extension; 
  • Each builder will have different circumstances that will effect their quote, even though the materials and work won’t change; 
  • Approaching only one or two builders could give you an idea of a false average building cost.

Get started in the form below.

Terms and conditions of use of the calculator, and FAQs.

Advice and tips for your extension budgeting: