Free building cost calculator
Find out what your building work could cost.
Get a free Guide Price—an early cost range for your extension, renovation or home improvements. See the breakdown, what could change the cost and what still needs checking.
What can you estimate?
UK projects include extensions, loft conversions, kitchens, bathrooms, renovations, basement work and new homes. Smaller jobs such as flooring, plastering and decorating are also covered.
Choose the project country when you start. Other countries have their own supported work and prices in local currency.
How it works
- Describe your project. Choose the work, its approximate size and location.
- Add what you know. Include finishes, changes to the existing building and anything that makes the work more involved.
- Review your Guide Price. See the range, breakdown and items still to confirm. Change the details to compare options.
You can start before every decision is made and update the price as your plans develop.
Built on real building experience
Proper Job is developed with hands-on experience in building, carpentry and project management. Its pricing considers the property, work involved, access, materials and associated work—not just floor area.
Building costs for your location
Each country uses its own pricing references and rules. Coverage varies by location; your Guide Price shows its assumptions and work still to price. Local quotes, taxes, approvals and site conditions still need checking.
Talk through your plans in ChatGPT or Claude
Connect Proper Job to a compatible chat to gather the project details and explore different choices. Proper Job calculates the price using its building cost data and pricing rules.
Add drawings for a Detailed Estimate
For UK projects, the paid service works from architectural PDF drawings. Review the measurements before they are used in itemised costing. Anything unmeasured or unpriced stays visible for checking.
Common questions
Is a Guide Price free?
Yes. Guide Prices and comparisons are free. Sign in to save your projects on the Proper Job website or apps.
Do I need drawings to get started?
No. Start with the type of work, approximate size and location. Add more details as your plans develop. Drawings help when you are ready for measured, itemised costing.
Why not just use a price per square metre?
A square-metre price is a starting point. Two projects of the same size can involve very different work. Walls, drainage, heating, access and finishes all affect the cost. A Guide Price uses the details you provide; more detail does not guarantee the final cost.
When do I need a Detailed Estimate?
For UK projects, use the paid Detailed Estimate service when your architectural PDF drawings and main decisions are ready. Review the measurements before they are used in the costing. Unmeasured or unpriced work stays clearly identified.
Is a Proper Job Guide Price a quote?
No. It is an early budget range to help you plan and compare scope. A builder still needs to check the property, drawings, specification, exclusions and current site conditions before giving a firm quote.