Garage Conversion Cost Calculator UK
Estimate the 2026 cost of converting your garage into a habitable room — by size, finish and region. Real building-quote figures with a realistic low–mid–high range. No email required.
Estimate Your Garage Conversion Cost
Choose your garage size, finish and region for an instant 2026 estimate.
How This Calculator Works
This calculator combines your garage size with a finish multiplier and real 2026 UK building-quote pricing, then applies a regional labour multiplier.
Size Base Prices (building work)
- Single garage ~£10,000
- Double garage ~£18,000
- Large / detached ~£24,000
- Finish: + en-suite / plumbing ×1.30 · + kitchenette / annexe ×1.55
Covers insulation, floor, new openings, heating, electrics and finishes — excludes furniture.
Regional Multipliers
- London 1.25× · South East 1.12×
- Midlands & East 1.00× (baseline)
- South West & Wales 0.95×
- North & Scotland 0.90×
Low/high reflect a ±15% spread around the mid estimate. A real quote follows a site survey.
Typical Garage Conversion Costs (2026)
Building work (insulation, floor, openings, heating, electrics, finishes; excl. furniture), Midlands baseline (±15%).
| Garage size | Finish | Cost range |
|---|---|---|
| Single | Habitable room | £8,500–£11,500 |
| Single | + en-suite / plumbing | £11,050–£14,950 |
| Double | Habitable room | £15,300–£20,700 |
| Double | + kitchenette / annexe | £23,715–£32,085 |
| Large / detached | Habitable room | £20,400–£27,600 |
These figures power the calculator above — enter your own spec for a tailored estimate. For the full breakdown, read our complete cost guide. Most garage conversions are permitted development, so you usually will not need planning permission — but you almost always need Building Regulations approval, because turning a garage into a habitable room means meeting standards for floor insulation and damp-proofing, wall and roof insulation, ventilation, fire escape and, where the up-and-over door is removed, a properly built and insulated infill wall on foundations. Flats, listed buildings, homes in conservation areas and any conversion into a separate dwelling are the common exceptions that do need a planning application. Budget for a building-control fee and, on integral garages, for raising the floor to clear damp. See our garage conversion planning guide and whether it is worth it in 2026.
Where the estimate ends and a survey begins
The calculator assumes a sound, standard garage, and most of the gap between its figure and a builder's quote comes down to what turns up once work starts. An integral garage — one built into the house — usually has its floor set below the level of the rooms next door and no damp-proofing under it, so that floor often has to come up, be tanked against damp and be relaid at the right height before the room is habitable. That one step can add a few thousand pounds, and it is the most common reason an integral conversion costs more than a detached one of the same size.
The other big variables are the foundations under the up-and-over door — the infill wall that replaces it has to sit on adequate footings — and whether the existing roof and walls can reach current insulation standards without being rebuilt. None of these show up in an online estimate; they show up in a site survey, which is why the figure here is a budgeting start point and the three quotes that follow it are the number you actually build to.
Frequently Asked Questions
How much does a garage conversion cost in 2026?
Do I need planning permission?
Does it need Building Regulations?
How long does it take?
Does it add value?
How accurate is this garage conversion cost estimate?
What does the garage conversion estimate include and exclude?
Why might a builder's quote exceed this estimate?
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