Using the Calculator
With our added value calculator you can input your desired size in metres, number of storeys and then location. The calculator will estimate the total value of the extension based on the regional price per square metre.
When inputting the extension size remember to use external dimensions, the calculator automatically calculates the correct floor area taking the wall thickness into account.
What you can also do is use our extension cost calculator to first work out the actual build cost and then determine the return on investment using the calculator below.
Return on Investment
Once you calculated the cost plus the estimated added value from the above calculator you can then determine your return on investment for the build. A good ROI would be in the region of 70%, but can vary greatly.
Sources
https://www.gov.uk/guidance/about-the-price-paid-data
https://epc.opendatacommunities.org/