If you’re thinking of extending your house, this free tool will estimate how much it is likely to cost. 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 as to how much your finished project should cost.

sloping site bungalow remodelled with a modern extension

The extension cost calculator is based on the very latest costs for materials and labour, and will provide you with cost estimates for:

  • Single-storey extensions
  • Two-storey extensions
  • Loft conversions
  • Garage conversions
  • Cellar conversions
  • Basement extensions

You can then fine-tune your estimate to match your needs, adding everything from your dream kitchen, bathroom, wet room or staircase, to the perfect bi-fold doors and statement windows. It will also advise you on the cost of essentials, like groundworks and utilities.

You can either start a new calculation or amend an existing one – receiving an estimate for your project in seconds.

Start estimating now