Defining a project construction budget and having awareness of average construction costs is one of the first steps to successfully designing a home. A realistic budget can help homeowners and clients decide between building a new bespoke home on an empty site, extend their existing property or keep the project to an internal remodel/retrofit. With that information at hand, it can be established if the client already has enough funds in place or if they need to seek additional funding where they can. The viability of a project relies on early stage financial planning, without that there can be extra expenses to redesign at a late stage, or worse, the project can run out of funds midway through construction. It is very important for architects and designers to be aware of the client’s budget and current construction costs so that they can advise the client on best options for successful project.
Estimate the cost of your home build or renovation project using our simple calculator below. Bear in mind that costs can vary significantly according to your specifications, property constraints and location. Our calculator is based on average UK construction costs data and is an early stage tool to be used as a rough guide.
If you are elsewhere in the world or would like to use it as a template for your own calculator you can purchase the original excel file on this link. This will have all the background data for you to access and edit for your own purposes.
Architecture students, other small architectural practices and other construction professionals, you are all very welcome here and we are happy to share this with you and hope this helps you in your studies and businesses.
Instructions on how to use the calculator can be found directly below the table.
How to use (this calculator is better viewed on a PC or laptop)
1 – Only edit light grey cells. Dark grey cells contain formulas and if edited the calculator will not work properly. If you have made a mistake just reload the page and you will have a fresh calculator to start again.
2 – Choose your location in the UK from the following options: “UK National Average“, “Inner London“, “Outer London“, “South East“, “South West“, “East Anglia“, “North West“, “North East“, “East Midlands“, “West Midlands“, “Yorkshire and the Humber“, “Wales“, “Scotland“, “Northern Ireland“. Use the drop down menu or just copy and paste the locations exactly as they a written here, make sure there are no spaces before or after the location name only in between words.
3 – Enter your property’s current market value, you can find this on sites like Zoopla. Or use the price you paid for it, if you recently purchased it or a recent valuation you received. This, together with build quality, is used to estimate the cost of fitting out kitchens and bathrooms.
4 – Choose the build quality of your planned works from the following options: “Basic build“, “Standard, high-quality build“, “Premium quality build“. If the drop down menu does not work for you, just copy and paste the build quality options exactly as they are written here, make sure there are no spaces before or after the copied text. Basic build would be a very simple geometry with standard materials and glazing, standard high-quality build is a mid range build with some special features and good quality materials, Premium quality build would be a high end design with architecturally designed special features and bespoke glazing throughout.
Get this calculator for excel/google sheets
5 – Choose the number of kitchens and bathrooms that will be refurbished or built as part of the project. This will add to the calculation the approximate additional cost of fitting out those rooms.
6 – Enter the approximate floor area of the building or refurbishment works in the appropriate cells. You can only use square meters as unit area, please convert before typing in. There are four types of build work included: New build, Refurbishment, Extension and Loft Conversion. New build is for buildings on empty sites or outbuildings. Extension is for new build areas of the works for the enlargement of a home. Refurbishment is for interior alterations only or for any areas that will be refurbished as part of a larger home extension project. Loft conversions is for work within your roof space. For example, the table is populated with a working example where there is a ground floor extension of 23m2. Additionally, two rooms which are part of the original footprint of the building with a total area of 20m2 will be refurbished as part of the works. It is more often than not that the total actual area of building works is much higher than the area of the extension and this is where most budget calculations get it wrong. Ignoring the works necessary within the existing footprint of the project, especially for the creation of open plan spaces is unwise, and will create budget issues and frustration for many homeowners. Make sure this is accounted for.
7 – The cost of new kitchens and bathrooms is automatically calculated for you based on the market value of the property and build quality. You don’t need to change this as this is an early stage budget estimator, but you can type a different percentage if you wish and this will override the formula applied to that cell.
8 – Assume at least 5%-7.5% extra cost for landscaping if you are just adding new decking or a simple patio but it could be anywhere between 5%-15% as an early stage estimation. If you also have a new driveway or more extensive road works the extra cost will be closer to 15% and even above for larger sites.
9 – Beside the cell “other” add any additional known costs as an equivalent percentage. Try different percentages and adjust until the dark grey cell shows a value close to what you want to insert. Do not use this for unknown costs. The contingency row should be used for that.
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10 – Apply the correct rate of VAT that applies to your work. Normally 20%, and you can use this as a basis and starting point, but can be 5% for properties that have been empty for more than 2 years in the UK. If your work is a self build you may be able to claim some of the VAT back so consider that when working out your percentage.
11 – Contingency – allow for at least 10% contingency for the works.
12 – Your costs with statutory fees and consultants will be approximately 10-15% of the “Construction Cost”. You can either just add 10-15% to it to simplify things as an initial budget or you can use the second part of the calculator to calculate this more accurately. This is another type of cost that sometimes is taken for granted by homeowners and although it is a relatively small percentage of the overall cost it can create stress on smaller budgets. Make sure to account for this. For each of the statutory fees and consultant costs there is a suggestion of cost, percentage or range, use these as a starting point and type zero whenever you are sure you will not require a certain service or fee.
13 – Remember to only edit the light grey cells and NOT the dark grey ones. Again, if you make a mistake such as editing the dark grey cells just refresh the page and the table will be fixed so you can start again.
14 – Thanks for using our calculator. We hope this will be a useful resource for your project!