Room by room estimator
Price a refurbishment, an extension or a conversion, one space at a time
Most cost calculators open on a six figure number for a job nobody asked for, because they price a whole building against an average. This one starts at nothing. Add a room, a garden, a loft or a roof, give it a size or keep the typical one, and tick the work you actually want doing in it. Every rate is measured against that space's own dimensions, and the total is the sum of what you chose and nothing else. Renovating, extending and converting all sit in the same estimate, because most real jobs are two of the three.
For: Anything from a single room to a whole house, extended or converted
What else to allow fornothing added
Where these figures come from
What the rates are. What a builder charges a customer for that item, fitted, excluding VAT, at a good domestic standard in the North West, which is where we work and the region every rate is quoted at. They already include labour, materials, the builder's overhead and the builder's margin, so nothing is added on top of them for those. Published UK cost guides at 2026 prices, cross-checked against what our own trades charge.
Labour and materials. A space priced as labour plus materials uses each work's labour-only rate, the same North West prices with the materials taken out, and lists the materials it takes at merchant prices per item, supply only, excluding VAT. A quantity is the space's measurement times a coverage rule — sixty bricks to a square metre of wall, a bag of plaster to ten — plus 10% wastage (10% unless you change it) for the cuts and the breakages, rounded up to whole units and to whole packs where it comes in one. Tick the materials off, or type the quantity you have counted, and the space uses yours.
How quantities are worked out. Floor and ceiling are length × width. The perimeter is twice length plus width. Wall area is the perimeter times the height, less 10% for the doors and windows in it. Anything priced one at a time asks you for the number.
The programme. Every work carries the hours a unit of it takes. A space's hours are added up and shown as eight-hour days; weeks are days divided by the crew times five. It is the labour on the space, one space after another, and not a promise about the order or the drying times.
What moves a rate. Three things only: where it is, the standard of finish, and the age of the building — and age only touches work on what is already standing. A material is not moved by any of them: a brick costs what the merchant charges. Listed buildings, restricted access and working round people who live there are all real costs, and they are priced as their own lines where they apply rather than as a silent percentage on everything.
Benchmarks to check the answer against. A bathroom refitted £5,500 to £11,000. A kitchen fitted £8,000 to £22,000. A full house refurbishment £900 to £1,800 a square metre. A single storey extension £2,000 to £3,000 a square metre all in, a two storey £1,600 to £2,500. A loft conversion £27,500 for a rooflight scheme, £40,000 to £70,000 for a dormer. A garage conversion £900 to £1,500 a square metre. New build £1,900 to £3,200.
VAT. A new dwelling is zero rated. A conversion that changes the number of dwellings, and a home empty for two years or more, are both at 5%. Everything else is standard rated. The contractor has to charge the right rate at the time with the evidence on file; it is not something reclaimed afterwards.
An estimate, and a desktop one: published rates measured against sizes typed into a form. It is a genuinely useful starting point and it is not a quotation, a tender or a valuation, and nobody here will put a firm figure on a building before they have stood in it. The rates exclude what nobody can see from a description — what is under the floor, what the drains are made of, what the last contractor did badly and what the ground is like. That is what the contingency is for. Where a survey follows, what comes back is a priced, tender ready schedule against these same lines rather than a condition report, and the fee for it comes off the build if you appoint us.
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The calculators that go with this one.
Each answers a single question, on its own page, with every figure in it yours to change.