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Know your numbers before you start.

A cost estimator, the verified builder directory, and plain-English guides — everything to plan a project before you speak to anyone.

Cost Planner

Indicative UK costs by project, size and region — in seconds.

Inspiration & guides

Real costs, planning pitfalls and how to sequence a project.

Cost Planner

UK-wide indicative costs. No commitment. Pick a project type, size and region for a realistic range.

Project

Approximate floor area

30 m²

Region

Best fit by postcode area, not a boundary-accurate lookup. Nothing is sent anywhere — this calculates in your browser.

Specification

Mid-range brands and finishes — what most projects use.

Specification picks which rate you're priced at. The range around the answer is a separate allowance for uncertainty.

Total to budget

£102,148

Typically £83,800 – £130,700

Extension · 30 m² · UK average · Standard materials

Builder's work: £70,500
Design, structural & building control: £6,300
Planning application: £548
VAT at 20%: £15,500
Contingency (10%): £9,300
Total to budget: £102,148

If the property has stood empty for two years or more, or the work changes the number of dwellings, VAT may be 5% rather than 20%. We can't verify that, so we've assumed 20%.

Materials ~

£35,300

Labour ~

£35,200

A split of the builder's work line only.

Indicative only — site conditions, access, materials and planning move the final figure. Builders price the project, not the range. This isn't a quote. Rates v5, reviewed August 2026. How we calculate this →

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Rates, not guesses

Each trade carries essential, standard and premium rates, re-based against named public sources. We don't hold a BCIS licence and don't claim one.

Region and spec do different jobs

Spec picks which rate you're priced at. Region multiplies it — London (inner) ×1.30, UK average ×1.00, North East ×0.94. The range around the answer is a separate allowance for uncertainty.

VAT, fees and contingency are shown

Published UK build-cost rates exclude VAT. We add VAT, professional fees, the statutory planning fee and a contingency — each on its own line, so you can see what makes up the total.

Read the full methodology

Every rate, multiplier and source we use is published, along with when it was last reviewed.

How we calculate this

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