How to Use TNK's Project Cost Calculator to Get a Realistic Ballpark
Before you spend time on drawings or quotes, it helps to know roughly what your project might cost. The TNK project cost calculator is designed to give you that early ballpark in a few minutes. This guide explains how to get the most from it, how to read the result and where it fits in the wider process.
What the calculator is for
The calculator gives an indicative figure so you can test whether a project is realistic for your budget. It is a starting point, not a fixed quote. Building costs depend on the details: the condition of the property, structural needs, specification, access and approvals. Only a site visit and itemised quote can pin those down, and we say so plainly.
Think of it as a planning aid. It helps you compare ideas, such as a loft conversion against an extension, before committing time and money.
Get ready before you start
A little preparation produces a more useful result. Gather:
The type of project: loft, extension, refurbishment, new build, fit-out or carpentry.
A rough size or scope, such as how many rooms and approximately what floor area.
Your property type, for example terrace, semi or detached, and its approximate age.
Whether you want extras such as a bathroom, kitchen or bespoke joinery.
The quality of finish you have in mind, from practical to high-end.
If you are unsure, use your best estimate, then try a few variations to see how the number moves.
Using the calculator step by step
Open the cost calculator and read any guidance on the page.
Select the type of project that is closest to what you have in mind.
Enter the details requested as accurately as you can.
Review the result as a range of what to expect, rather than a single figure.
Re-run it with different options, such as a higher or lower specification, to see how choices affect the outcome.
Make a note of your results to bring to a conversation with a builder.
How to read the result
Treat the output as a guide to the order of magnitude. A few points to keep in mind:
It is indicative. Actual prices vary with site conditions, structure and finishes.
It may not include everything. Design fees, building control, Party Wall costs, VAT where applicable, furnishings and a contingency may sit outside a build figure. Ask what is and is not covered.
Ranges beat single numbers. If the result looks higher or lower than you expected, ask why.
Compare like with like. When you receive quotes, check they match the scope you had in mind.
We also suggest adding your own contingency on top of any estimate. Our guide to refurbishment contingency explains how to think about that, and a typical rule of thumb is around 10 to 15 per cent for many projects.
What to do after you have a number
Once you have a ballpark, the next steps usually are:
Decide whether the figure fits your budget, or whether you need to adjust scope.
Think about the type of project that suits your house. See our pages on loft conversions and extensions.
Check planning and building regulations requirements with your local council.
Book a site visit so the numbers can be firmed up.
Ask for an itemised quote with a clear specification.
A sensible habit is to run the calculator more than once. Try a basic scenario, then a version with a higher specification, then one with extras such as a bathroom or bespoke carpentry. Seeing how the numbers shift tells you where your money is going and which choices matter most. If you are deciding between a loft and a rear extension, run both and compare the ballparks alongside what each adds to your home.
When you speak to our team, bring your results. They give us a useful starting point for the conversation, and they let you ask better questions about what drives the difference between an early estimate and a firm quote.
Remember that the calculator is only one input. Combine it with a conversation about your goals, a site visit and your own contingency, and you will have a much more reliable picture of what your project is likely to involve.
Frequently asked questions
Is the calculator a formal quote?
No. It gives an indicative figure only. A formal quote follows a site visit and agreed drawings and specification.
Why might my final quote differ?
Structure, access, finishes, approvals and changes in scope can all move the price, in either direction.
Do I need to have drawings first?
No. The calculator is designed for early planning, before drawings exist.
Try it, then talk to us
Open the TNK cost calculator to get your first ballpark, then contact our team and we will help you turn it into a realistic plan.
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