Extension Cost Calculator: How Much Will Your Build Cost?

extension cost calculator Blue Shaker kitchen with large central kitchen island
(Image credit: Oliver and Barr)

Looking to extend? Then our free extension cost calculator will help you get an idea of costs for your build. And it takes a matter of minutes to do.

Before you go ahead and start building an extension you'll need to know how much the project is likely to cost before you commit.

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Garage Cost Guide (gross external floor area)
Row 0 - Cell 0 StandardGoodExcellent
Single Garage - Detached 17m²£12,800 £13,700£15,800
Single Garage - Attached 15m²£10,500£11,700£13,700
Double Garage - Detached 31m²£17,300£18,300£21,700
Double Garage - Attached 30m²£15,400£16,100£19,100
Jason Orme
Managing Director

The former Editor of Homebuilding & Renovating magazine, Jason is an experienced self builder and has recently finished renovating his 1960s home. Jason is now Managing Director of Future PLC's Homes' portfolio, which includes UK-leading titles such as Ideal Homes, Livingetc and Homes & Gardens. He is also the author of The Self Build Dream. You can catch Jason in the seminar theatres and Advice Centre at many of the Homebuilding & Renovating Shows across the UK.