Know exactly what your
extension will cost.
A ready-made budget spreadsheet with every cost category pre-populated. Fill in your quotes, and it calculates your total budget with contingency automatically.
Every cost category for a UK kitchen extension.
Builder's work
Foundations, blockwork, roof, steelwork
Electrics & plumbing
First fix, second fix, underfloor heating
Kitchen supply & fit
Units, worktops, appliances, fitting
Professional fees
Architect, structural engineer, building control
Windows, doors & glazing
Bifolds, roof lanterns, standard windows
Finishes
Plastering, tiling, flooring, decoration
Automatic calculations built in
- Contingency at 15% and 20% (choose which to use)
- Total project budget including contingency
- Build-only and all-in cost per m²
- Regional benchmark comparisons on a separate tab
The average kitchen extension costs £40–80k.
Most homeowners don't track costs properly until they're already over budget. This spreadsheet gives you a realistic picture from day one — before the first quote comes in.
14
Cost categories
Auto
Contingency calc
£/m²
Regional benchmarks
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Three steps to a realistic budget.
Enter your extension floor area
The spreadsheet uses this for cost-per-m² calculations and regional benchmarking.
Fill in quotes as you get them
Use the estimate column for ballpark figures early on. Replace with actual quotes as they arrive. Leave categories blank until you have a real number.
Check your total against regional benchmarks
The separate benchmarks tab shows typical all-in costs per m² for UK kitchen extensions. If your number is wildly different, investigate why.
Works in Excel, Google Sheets, and Numbers. Free to download.