Garage Conversion Cost Calculator: An Indicative London Budget
Last reviewed: 6 November 2026
Enter the conversion scope and the floor area you want to convert. The calculator scales the single-garage totals published in our garage conversion cost guide, adds the London allowance taken from the same guide's regional table, and shows an indicative range. Every figure includes VAT at 20%. It is a budgeting tool, not a quote.
Garage conversion cost estimator
Indicative only — including VAT, before professional fees and contingency. Confirm a written scope and itemised quote.
How to use this estimate: enter the floor area you want to turn into habitable space — for a single garage that is usually 15–20 m², for a double 30–40 m². A typical single garage is 20 m², which is where this calculator's rates are anchored. The London allowance adds 20% to the lower rate and 25% to the upper rate.
What this range includes and excludes
- Includes VAT at 20%. Our garage conversion cost guide states all of its prices including VAT, so the calculator does too — unlike our extension calculator, which works before VAT.
- London allowance: +20% on the lower rate and +25% on the upper rate, derived from the guide's London & South East row (£24,000 – £35,000 for a standard single conversion) against its national standard single row (£20,000 – £28,000). The guide publishes London and the South East together, so for central London this may be conservative.
- Excludes: professional fees, building control, planning fees, party wall costs and contingency. It also excludes remedial structural work — underpinning, extensive damp work, asbestos removal — which the guide prices separately.
- Larger garages: the guide's double-garage rows come out a little below this per-square-metre model because fixed costs spread further. For a garage over 30 m², treat the guide's double-garage table as the closer reference.
- Not a price: the result is rounded to the nearest £1,000 and is a budgeting range, not a quotation.
Rates used in this calculator
| Conversion scope | Published total for a single garage (15–20 m², incl. VAT) | Same total as a rate per m² at 20 m² |
|---|---|---|
| Basic conversion — shell only, minimal finish | £15,000 – £20,000 | £750 – £1,000 |
| Standard conversion — insulated, plastered, electrics, flooring | £20,000 – £28,000 | £1,000 – £1,400 |
| High-end conversion — bespoke finish, integrated utilities | £28,000 – £40,000 | £1,400 – £2,000 |
How the per-square-metre rates were derived
Our guide states a standard garage conversion at £900 – £1,400 per m² and high-end work at £1,600 – £2,000 per m², and it also publishes the single-garage totals shown above. Those two ways of stating the same thing do not reconcile exactly: £900 – £1,400 per m² at 20 m² would be £18,000 – £28,000, while the guide's standard single-garage total is £20,000 – £28,000. This calculator anchors on the published totals, because they are the figures that pair with the guide's London & South East row and reproduce its worked examples exactly. That is why its lower rate is £1,000 per m² rather than £900.
| What our garage conversion cost guide also states | Figure |
|---|---|
| Standard garage conversion, per m² | £900 – £1,400 (incl. VAT) |
| High-end finish or complex structural work, per m² | £1,600 – £2,000 (incl. VAT) |
| London & South East, standard single garage conversion | £24,000 – £35,000 |
| London & South East, labour rate for a builder | £250 – £350 per day |
| Partial conversion, half of a double garage (15 m² habitable) | £12,000 – £18,000 |
| Partial conversion, two-thirds (20 m² habitable, 10 m² storage) | £16,000 – £24,000 |
Worked examples from our published guide
The figures below are the guide's own published totals, recalculated from the rates above.
| Published example | Our guide says | Calculator's rates give |
|---|---|---|
| Basic conversion (shell only, minimal finish), 20 m² | £15,000 – £20,000 | £15,000 – £20,000 |
| Standard conversion (insulated, plastered, electrics, flooring), 20 m² | £20,000 – £28,000 | £20,000 – £28,000 |
| High-end conversion (bespoke finish, integrated utilities), 20 m² | £28,000 – £40,000 | £28,000 – £40,000 |
| Standard single garage, London & South East, 20 m² | £24,000 – £35,000 | £24,000 – £35,000 |
Frequently asked questions
How much does a garage conversion cost per square metre?
Our garage conversion cost guide states £900 to £1,400 per m² for a standard conversion and £1,600 to £2,000 per m² for high-end finishes or complex structural work, both including VAT at 20%. The same guide publishes single-garage totals of £15,000 to £20,000 basic, £20,000 to £28,000 standard and £28,000 to £40,000 high-end for a 15 to 20 m² garage. This calculator is built on those published totals.
Does this calculator include VAT?
Yes. Every figure includes VAT at 20%, because that is how our garage conversion cost guide states its prices. It is before professional fees, building control, planning fees, party wall costs and contingency.
Why does the London figure differ from the national one?
Our garage conversion cost guide publishes London and the South East as a single regional row: £24,000 to £35,000 for a standard single conversion, against £20,000 to £28,000 nationally. The calculator applies that difference as +20% on the lower rate and +25% on the upper rate. Because London and the South East are published together, central London may sit above this range.
Can I keep part of the garage for storage?
Yes, and it costs less. The guide's partial-conversion figures are £12,000 to £18,000 for half of a double garage (15 m² habitable) and £16,000 to £24,000 for a two-thirds conversion (20 m² habitable with 10 m² of storage), including VAT.
Is this a quote?
No. It is an indicative range from published rates. The condition of the existing garage, the services route, access and the finish you choose all move the number. The next step is a free survey and a written, itemised quotation.
Plan your London garage conversion
Discuss your property, the existing garage and next steps at a free survey.
Book a free survey →Prefer to read the workings? Read the full garage conversion cost guide.
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