Loft budget planner
Loft Conversion Cost Calculator UK
Get an indicative cost range for your loft conversion project. Choose the conversion type, size, specification and location for a UK market estimate.
Typical project budget
£20,000–£90,000+
Biggest cost drivers
Conversion type, stairs, en-suite, planning
Best use
Comparing loft options before design fees
Finished loft example
Useful for picturing the end result — but the structural route is what really drives the budget.
Loft cost snapshot
Dormer vs mansard is usually the biggest budget fork
Use the calculator to compare conversion routes, then check the loft types and cost-per-m² guides before you commit to plans.
Remember
Staircase design, steelwork and en-suite plumbing can change the economics more than cosmetic finishes do.
Good next step
Compare the loft route against an extension if you are choosing where to add space.
Estimated Loft Conversion Cost
Indicative range. Not a quote. Includes a 10% contingency.
Cost Breakdown
| Structural Works | — |
| Staircase | — |
| Plumbing & Electrical | — |
| Admin & Permissions | — |
| Contingency (10%) | — |
| Estimated Total | — |
How We Estimate
- • Estimates assume a standard UK semi-detached or terraced property. Flats and end-terrace properties may have different structural requirements.
- • Prices include design, structural engineer, building control and all trades.
- • Loft conversions typically require Building Regulations approval even under Permitted Development.
- • This is an indicative estimate, not a quote.
- • Last updated: Q2 2026.
Calculate More
Understand Your Loft Conversion Cost
Quick answers for UK homeowners
How much does a loft conversion cost in the UK?
Most UK loft conversions fall into a broad range depending on size, structure, access, dormers, bathrooms and finish level. Use the calculator as a planning estimate before getting fixed quotes.
What affects the cost most?
The biggest cost drivers are conversion type, roof structure, floor strengthening, staircase position, insulation, windows and whether you add a bathroom.
Is this a replacement for a builder quote?
No. It is a budgeting tool to help you understand likely ranges and compare options before speaking to builders or designers.
Related planning pages