Good candidate
Dry structure, sound roof, reasonable floor level, simple access to electrics and a clear plan for replacing the garage door.
Garage conversion costs
Garage Conversion Cost Calculator UK
Estimate the cost of converting a garage into usable living space. This calculator uses garage size, garage type, planned use, existing condition, finish level and region to produce a realistic UK cost range.
This calculator is part of the extensions cost section. If you are comparing a garage conversion with building new space, use the single storey extension cost calculator or loft conversion cost calculator.
Use this estimate before speaking with builders
A garage conversion usually starts with a structure that already exists. That can reduce the cost compared with a new extension, but only if the garage is dry, structurally sound and suitable for the room you want to create. This estimate helps you separate a straightforward conversion from a project that may need remedial work first.
Is your garage a good conversion candidate?
The best garage conversions start with a dry, sound structure that can be insulated, heated and connected to the home without major changes. Integral garages are often easier because they are already part of the main house. Detached garages need closer checks around services, weatherproofing and access.
A low quote is not useful if the finished room still feels like a cold converted garage. The aim is to create space that works as part of the home, with proper floor levels, ventilation, natural light, heating and insulation.
Needs closer checking
Damp patches, low floor levels, poor ventilation, old roof coverings or limited access to heating and electrics.
Higher-risk conversion
Detached, poorly insulated or service-heavy projects where drainage, heating and structural condition are uncertain.
What type of garage conversion are you pricing?
The planned use affects the amount of work needed. A home office may need insulation, electrics, heating and finishes. A shower room, utility or annexe-style space adds services and more compliance checks.
Home office or hobby room
Usually the simplest use because plumbing is often not needed. Comfort still depends on insulation, heating, ventilation and natural light.
Bedroom or living room
Needs a warmer, more finished feel. Floor level, windows, heating, lighting and connection to the house become more important.
Utility or shower room
Plumbing, drainage, ventilation, waterproofing and service routes can move the cost above a basic room conversion.
Annexe-style space
The highest-cost route. It may need more privacy, heating, services, drainage, storage, finishes and closer design checks.
Typical UK garage conversion cost ranges
Use these ranges as a planning guide. Your garage condition and intended room use can shift the result more than the headline size.
| Garage conversion type | Typical size | Estimated range | Why the cost moves |
|---|---|---|---|
| Basic single garage office | 12–18 m² | £12,000–£28,000 | Lower services, simpler fit-out and limited plumbing. |
| Single garage living room | 12–20 m² | £18,000–£40,000 | Insulation, heating, windows, flooring and finish level shape the range. |
| Garage with utility/shower room | 15–25 m² | £25,000–£55,000 | Plumbing, drainage, ventilation and waterproofing add cost. |
| Double garage conversion | 28–36 m² | £30,000–£75,000 | Larger area gives more layout options but increases fit-out and services. |
| Detached garage conversion | 15–35 m² | £25,000–£80,000+ | Services, heating, weatherproofing and access can add significant cost. |
The hidden cost question: is the garage already room-like?
A garage can look like cheap space because it already has walls and a roof. The real cost question is how much work is needed to make it feel like part of the home rather than a finished garage.
Floor level, damp protection, ventilation, insulation and natural light all matter. Replacing the garage door with a wall, window or entrance can also affect the final look and cost. If heating and electrics are close, the conversion may stay straightforward. If plumbing, drainage or roof repairs are needed, the budget can change quickly.
What affects garage conversion cost?
Garage conversion costs are usually driven by the gap between the existing garage and the finished room you want. The biggest changes often come from comfort, condition and services.
Garage door infill
Replacing the garage door with a wall, window or door is one of the most visible changes. It affects cost, daylight and how well the room blends with the house.
Insulation and damp protection
Garages are often not built to the same comfort standard as living rooms. Walls, floors and roofs may need upgrading before the space feels usable year-round.
Floor level and finish
The floor may need raising, insulating, levelling or damp-proofing. This can affect doors, thresholds and the transition into the main house.
Services
Electrics, heating, plumbing and drainage vary widely depending on whether the room is a simple office, bedroom, utility or annexe-style space.
If the project includes a shower room or utility, compare related service costs with the bathroom plumbing cost calculator and kitchen plumbing cost calculator.
Garage conversion vs extension
A garage conversion often costs less than building new space because the structure may already exist. An extension is usually better when the home needs a larger kitchen, dining area or major new living space.
| Factor | Garage conversion | Extension |
|---|---|---|
| Uses existing structure | Yes | Usually no |
| Adds footprint | No | Yes |
| Typical cost | Lower | Higher |
| Best for | Office, bedroom, utility, playroom | Kitchen, living space, major expansion |
| Main risk | Existing condition | Groundworks and structure |
Compare building new space with the single storey extension cost calculator or home extension cost calculator.
Garage conversion vs loft conversion
A garage conversion often creates ground-floor space with easier access. A loft conversion may be better when the goal is an extra bedroom or office upstairs and the garage is still needed for storage or parking.
If you are deciding between existing-space options, compare this result with the loft conversion cost calculator.
Cost per square metre needs context
Garage conversions can look expensive per m² because many projects are small. A single garage may only be 12–18m², but it still needs door infill, insulation, flooring, electrics, heating, plastering and finish work.
Use cost per m² to compare options, but judge the project by the final room created. For broader floor-area comparison, use the extension cost per m² calculator.
Why small conversions vary
Small floor areaHigher per m²
Fixed upgradesStill needed
Good structureCost advantage
What to prepare before getting quotes
Before requesting quotes, measure the garage floor area and decide how the room will be used. Note whether the garage is integral, attached or detached, whether plumbing is needed and whether there are signs of damp, roof wear or uneven floor levels.
It also helps to decide what should replace the garage door. A simple wall and window may be enough for some rooms. Other projects need a door, larger glazing or a layout that changes how the front of the property looks.
Quote-ready summary
Example brief: 18 m² integral garage conversion, home office / basic room, good condition, standard finish, Rest of England pricing, VAT included and 10% contingency.
Alternative projects worth comparing
If the garage is still needed for storage or parking, compare other ways to create space before converting it. The best alternative depends on whether you need upstairs rooms, ground-floor living space or a larger whole-home change.
Loft conversion
Compare this when the main goal is an extra bedroom, office or en-suite upstairs.
Single storey extension
Useful when the goal is a larger kitchen, dining area or ground-floor living space.
Double storey extension
Compare this when you need both downstairs and upstairs space.
Basement conversion
Relevant where below-ground space is possible, but structure and waterproofing need careful allowance.
Related cost calculators
Use these calculators to compare a garage conversion with related project costs and likely fit-out items.
Home extension
Broad estimate across common UK extension types.
Loft conversion
Compare roof-space conversion with garage conversion.
Extension cost per m²
Compare costs by floor area and total budget.
Flooring cost
Estimate flooring costs for the finished converted room.
Plastering cost
Useful where the garage needs walls and ceiling finished.
Painting cost
Estimate decorating costs once the room is ready.
Rewiring cost
Compare electrical allowances for lighting, sockets and circuits.
Bathroom renovation
Relevant if the garage conversion includes a shower room.
Garage conversion cost FAQs
How much does a garage conversion cost in the UK?
A garage conversion commonly ranges from around £12,000 for a simple office-style conversion to £75,000 or more for larger, detached or service-heavy projects.
Is a garage conversion cheaper than an extension?
Usually, yes. A garage conversion can be cheaper because the structure may already exist. Costs rise when damp work, insulation, floor upgrades, roof repairs, heating or plumbing are needed.
What is the cheapest type of garage conversion?
A simple integral garage conversion into an office or hobby room is usually the cheapest because it often needs fewer service changes than a bedroom, bathroom or annexe-style space.
Does converting a detached garage cost more?
Often, yes. Detached garages can need more work around electrics, heating, insulation, weatherproofing and access.
Does a garage conversion need plumbing?
Only if the room includes a utility, shower room, toilet, kitchen area or similar service-heavy use. Plumbing and drainage can add a significant amount to the cost.
Why can a small garage conversion cost more per m²?
A small garage still needs door infill, insulation, flooring, electrics, heating, plastering and finish work. These fixed costs are spread across a small floor area.