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Garage conversion cost calculator for UK builders.
Size it, check it against published averages, then price it from your own rates.
Quick answer
Pick the garage type, enter the floor area and see what published UK averages suggest homeowners pay. Checkatrade's 2026 guide puts a typical 16 m² attached garage conversion at around £15,000, and garage conversions in general at about £625 to £1,250 per m². Then enter your own build cost per m², preliminaries, contingency, markup and VAT to see your price and how it compares. The average is a sense-check. Your price comes from your own rates.
Source note: Averages come from Checkatrade's "Garage conversion cost in the UK in 2026" (tables last updated May 2026). VAT points come from HMRC VAT Notice 708 (last updated 26 August 2026) and GOV.UK's VAT rates page. Figures checked 26 October 2026. Checkatrade calls them ballpark averages and heads its price column "Cost + VAT". The calculator scales Checkatrade's averages to your floor area and rounds to the nearest £50. That scaling is our arithmetic.
Garage conversion cost calculator
Use square metres and the garage type to rough out the job before doing a full quote.
Published average for this size
£15,000
Published range
£10,000 to £20,000
Checkatrade averages (May 2026), scaled to your m². What homeowners typically pay, not your cost.
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Published averages by garage type
Checkatrade's figures (last updated May 2026), based on a 16 m² garage unless stated:
| Garage type | Average | Range |
|---|---|---|
| Integral | £12,000 | £10,000 to £14,000 |
| Attached | £15,000 | £10,000 to £20,000 |
| Detached | £20,000 | £15,000 to £25,000 |
| Double (36 m²) | £32,750 | £20,500 (integral) to £45,000 (detached) |
| Partial conversion | £7,000 | £5,500 to £8,500 |
Checkatrade says these assume insulation and screed can go over the existing slab, the services are suitable and the structure is sound. They include blocking up the door opening, battening and insulating the external walls and a basic fit-out. They exclude moving meter boxes, cutting new doorways in external walls, and kitchen or bathroom fittings. Price those separately if the job needs them.
Where the money goes
Checkatrade's structural and building cost lines (May 2026) make a useful checklist for your quote sections:
| Line | Checkatrade range |
|---|---|
| Remove and replace garage door | £1,300 to £1,500 |
| Door and window addition | £1,200 to £1,500 |
| Flooring (slab) | £1,000 to £1,250 |
| Stud wall | £750 to £950 |
| Electric socket | £90 to £100 |
| Pipes | £1,000 to £3,000 |
| Standard conversion total | £5,000 to £7,800 |
The guide also lists extras that sit outside the main price: architect drawings (around £2,000), structural engineer fees (£500 to £1,000), Building Regulations approval, party wall matters and waste removal. Price each line from your own labour, materials and subcontractor rates. If a line is far from the published figure, check the scope rather than copying the number. To lay it out for the client, use the garage conversion quote template.
What a clear garage conversion quote covers
Checkatrade tells homeowners to look for these in a quote: structural work, insulation, damp proofing, garage door removal, windows and doors, flooring, electrics, heating, plumbing if needed, plastering and decorating, waste removal, Building Regulations support, VAT, exclusions and the timescale. It also tells them to ask why one quote is much cheaper than another. Put each item on its own line, or list it as an exclusion, and your quote answers that question before it's asked.
Planning, Building Regulations and VAT
Planning: Checkatrade says planning permission isn't usually needed if the work is internal and doesn't enlarge the building, but may be needed for a detached garage, a big change to the outside, a listed building, a conservation area, an estate with restrictions, a separate dwelling, or where permitted development rights have been removed. Building Regulations approval is still needed, because the garage becomes a habitable room.
VAT: HMRC VAT Notice 708 says work to an existing building is normally charged at the standard rate, which is 20%. The 5% rate covers specific cases, such as creating a different number of dwellings. A garage turned into a room in the same house usually isn't one of them, but check the notice for your job. For quote wording, see VAT quote wording.
Primary sources
FAQ
How much does a garage conversion cost per m² in the UK?
Checkatrade's 2026 guide gives about £625 to £1,250 per m², based on £10,000 to £20,000 for a 16 m² garage. Use it to sense-check, not to set your price.
How much does a single garage conversion cost?
Checkatrade puts a 16 m² attached garage at around £15,000 (range £10,000 to £20,000), an integral garage at around £12,000 and a detached garage at around £20,000 (tables last updated May 2026).
How long does a garage conversion take?
Checkatrade says around 2 to 4 weeks for most garage conversions, depending on the garage type, its condition and the work involved.
Do I charge VAT on a garage conversion?
Usually at the standard rate. HMRC VAT Notice 708 says work to an existing building is normally standard-rated. Check the notice if the job creates a separate dwelling.
Can this calculator replace a site visit?
No. It sizes the job and compares it with published averages. The slab, walls, damp, services and access all need checking on site before you send a price.
Turn the rough number into a real quote.
Put in your own labour, materials and subcontractor rates for each section, add overhead, contingency, markup and VAT, and see a quote outline. It's free and you don't need to sign up to see the result.
Build a quote with your own rates