Architect Your Home With Architects Near Me – Sustainable Architects

Extension Cost Calculator

Residential Build Costs Calculator

This extension cost calculator provides a helpful tool for assessing the financial outlay required for your building project. It breaks down the various elements that make up the total price, allowing you to see how various factors impact your extension cost per square metre.

Whether you’re planning a single storey extension or something bigger, this tool will enable the calculation of a sensible estimate of your house extension cost per m2, whatever size and specification of extension you are planning.

Needing to Calculate Architect Fees?

Architect Your Home also offers an architects fee calculator to complement this extension cost calculator. Combine these 2 online calculators to help you estimate the entire cost of your refurbishment or home extension project.


Architects Fee Calculator

Use our Extension Cost Calculator UK to get an Estimate

Answer these 9 questions and submit your contact details for a no obligation estimate for your project. Only takes a few minutes to complete
Either is fine, our tool will give you an accurate estimate whichever option you choose.
If your project includes any areas of “new-build”construction such as a kitchen extension to the side or rear of your home, a new basement or maybe a garden out-building, please enter the floor area of this part of the project.
Sq. M
If your project includes any remodelling of existing space involving some construction such as a new staircase, knocking through a wall or removing a chimney breast etc., please enter the floor area of this part of the project.
Sq. M
Including all the above areas, please enter the total floor area to be fitted out? Fitting out work includes such things as heating, kitchens, painting & decorating, floor finishes, bathrooms, joinery, lighting & electrical work etc.
Sq. M
Are you looking for a basic job or something more high spec? Labour intensive fine finishes & expensive or bespoke components will be more costly than basic items available off the shelf at the builder’s merchant.
Basic High Specification
Are the proposals simple and straight-forward to build? Do the works involve complex structural or constructional difficulties or a great deal of ground-work and excavation? How easy is working access to the site and how much space will there be to operate?
Straight Forward Complex
Different builders can give radically different prices on the same specific proposals. Generally the better quality of work and the better organised they are, the more expensive they will be. Low cost will usually mean a compromise on quality, organisation or both.
Low Cost High Quality
Not only will local rates of pay vary regionally across the country (which will affect your builder’s costs), but also the reality is that builders will generally charge more when the project is located in a more expensive residential area that in a lower cost area.
Affordable Expensive
How much involvement are you planning for architects/designers for this project?
Not at all Intensive Involvement

Projected total cost

Based on the information you have given, your estimated build cost has been calculated as:


Ensure you allow for VAT, professional and application fees as well as a contingency sum.
If you would like help or advice with this form please call us on 0800 849 8505.

How Much Does an Extension Cost?

When planning an extension or renovation, it’s vital to grasp all the factors influencing the costs from the beginning. Understanding these elements helps avoid expensive errors later in the project.

Your architect plays a crucial role in helping you realise your dream space while staying within budget. Their extensive knowledge and experience will not only reveal what’s achievable but will also guide you through the expected financial implications, highlighting potential pitfalls to avoid.

A lot of the budget variance depends on you and the choices you make. With the help of our construction cost calculator, this cost estimator will help you get an idea of what you might have to spend. Our online estimator allows for dynamic adjustments—if the figures are higher or lower than your expectations, you can easily modify your inputs to see how changes affect the cost. This flexibility ensures you can continuously refine your plans until they perfectly align with your financial boundaries.

Need any further help, other information or assistance? Please get in touch below


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