Extension Cost Calculator

Simply select the type of renovation you are doing, rooms you are renovating, and input your postcode, then press 'Update'. Then by using the 'Customisation options', you can select your overall finish quality and input the size of your renovation.

Customisation options

Your cost breakdown


Customisation options


Overall finish quality

Low-end
Low-end
Mid-end
High-end
2640
3250
3890

Your cost breakdown


15
Professional fees*
(15%)
Labour and build cost
45
90
130
Windows and doors
25
45
70
Heating
58
130
185
Decor and finishing
17
Contingency*
(17%)

Total cost estimate (inc VAT)

£0

This is a high-level budgeting estimate, not a quotation.

For businesses

Want a calculator like this on your website?

Love Renovate creates and licenses branded renovation calculators for architects, builders, home-improvement businesses and larger organisations.

How to use our extension cost calculator

Use your estimate as a starting point for setting a realistic budget and comparing different versions of your extension. It is designed for early planning, before you have detailed drawings and quotations.

What your estimate includes

Your breakdown covers professional fees, labour and building work, windows and doors, heating, decorating and finishing, contingency and VAT.

How your project changes the cost

The estimate responds to your location, extension type, floor area, rooms and finish level. Adjust these details to compare different specifications and project sizes.

What can affect the final price

Site access, structural complexity, glazing, materials and the detail of your design can all affect quotations, as can local labour costs and unexpected work.

What the estimate cannot predict

Every property and design is different. The calculator cannot identify hidden structural problems, unusual ground conditions, difficult access, planning requirements or bespoke design details. Treat the result as an initial budgeting guide rather than a quotation, and base your final budget on a developed design and quotations for your property.

Extension cost calculator FAQs

How accurate is the extension cost calculator?

It provides an early estimate based on the project information you enter. It cannot replace drawings, a detailed specification or quotations from professionals and contractors who have assessed your property.

Does the extension estimate include VAT?

Yes. The total shown by the calculator includes VAT. Your eventual VAT treatment and costs should still be confirmed against the quotations you receive.

Are professional fees included?

The cost breakdown includes an allowance for professional fees. The actual amount will depend on the services your project needs and the professionals you appoint.

Does the estimate include a contingency?

Yes. A contingency allowance appears within the breakdown, but it cannot guarantee that every unexpected cost will be covered. Discuss an appropriate contingency with your architect or builder.

Why does location affect extension costs?

Labour rates and building costs vary across the UK. Entering your postcode allows the calculator to reflect regional differences when producing your initial estimate.

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