Fill in the dimensions for your job - length, width, height, or whatever fields the calculator asks for. All measurements are in metres and millimetres unless stated. Want a head start? Try a Quick Start Project Kit - pre-built job templates that load common specs in one click.
2
Adjust the waste allowance
Most calculators include a waste percentage field. The default is a recommended starting point - increase it for complex cuts or awkward layouts, reduce it for simple runs.
3
Click Calculate
Your material quantities appear instantly. Results show packs, bags, or units needed, plus the total area or volume for reference.
4
Add UK market prices (optional)
Click Get UK Market Prices if the option appears. This loads current trade rates and gives you a cost estimate alongside your quantities. You can edit any of the prices before calculating if your own rates differ.
5
Save to a project
Click Save to Project to store these results. You can create a new project or add the line to an existing one. You can save one project for free, or upgrade to a Pro account to store as many as you need with cloud backup and access across all your devices.
6
Print or export
Use the Print or Export CSV buttons to save your results. The print layout is clean and formatted for site use or handing to a client.
Your saved projects are under My Projects in the menu. Each project collects all your calculator results in one place - handy for pricing up a full job. You can freely amend any part of a project at any point. With a Pro account you can also send polished quotes to clients or material specs direct to subcontractors.
Not sure what self-build costs? Tell us what an equivalent house sells for near you - we'll do the rest.
Why self-build is cheaper than buying
When a developer builds and sells a house, they factor in their profit margin - typically 20-25% of the sale price. When you self-build, you capture that margin yourself. You also pay Stamp Duty only on the land, not the finished value, and you can reclaim VAT on eligible construction costs after completion. The result is that a self-built home typically costs 15-30% less to create than its market value - and it is built exactly to your specification.
20-25%
Developer profit margin you capture by self-building
0%
VAT on eligible self-build construction costs (reclaimable)
Land only
SDLT applies only to plot purchase, not finished value
100%
Custom - every design decision is yours to make
The house you have in mind
£
Estimated floor area: ~100 m²
Where are you building?
Land typically ~28% of completed value in this region
What kind of build?
Estimated saving vs buying
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You could build an equivalent home for significantly less than the asking price - and own a brand new property built exactly to your specification.
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less than buying
-
VAT reclaim (approx)
Full Cost Breakdown
Land / Plot
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Estimated plot cost for your region
Build Cost
-
Materials and labour
Professional Fees
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Architect, structural engineer, planning, surveys
Contingency
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15% reserve - always budget this on a self-build
Insurance & Warranty
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Site insurance, structural warranty (e.g. NHBC)
Planning & Building Control
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Application fees and building control inspections
VAT Reclaim (after completion)
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Reclaimable via HMRC DIY Housebuilders Scheme
Total Project Cost
-
vs - to buy
Where the money goes
About these estimates: Land cost is estimated as a percentage of completed value based on regional averages - actual plot prices vary widely even within a region. Build cost uses a per-m² rate for your chosen spec applied to an estimated floor area for your bedroom count. Professional fees are estimated at 12% of build cost. Contingency is 15% of build cost. VAT reclaim is estimated at 15% of build cost (eligible materials only - actual figure depends on your material spend). These are indicative figures to help you understand the rough shape of a self-build project. Always get detailed quotes from professionals before committing.
This tool gives you a broad-brush indication of the shape and scale of a self-build project - enough to understand whether it is financially viable for you. It should not be used for budgeting purposes. Land prices vary enormously even within a region - a plot with planning permission in a sought-after village can cost twice as much as one on the edge of a nearby town. Build costs also vary significantly depending on your exact design, your chosen contractor or package route, and regional labour rates. Before committing to anything, get a proper site appraisal from a local estate agent or land agent, and a preliminary cost plan from a quantity surveyor or self-build package company.
Why does land cost such a high percentage of the total?
Land with planning permission is priced by the market based on what can be built on it and what those homes will be worth when finished. In high-value areas like London and the South East, land is scarce and expensive, so it represents a larger share of the total project cost. In lower-value regions, land is cheaper in absolute terms but may still represent 20-25% of project cost. This is one reason self-build is relatively more financially rewarding in higher-value areas - the developer's profit margin you capture is larger in absolute terms.
What is the VAT reclaim and how does it work?
Under HMRC's DIY Housebuilders Scheme (VAT431NB), self-builders can reclaim VAT paid on eligible building materials after they receive their completion certificate. This is a one-time claim and must be submitted within three months of completion. You cannot reclaim VAT on professional fees, plant hire, or some materials - the eligible items are broadly the materials that become part of the permanent fabric of the building. Keep every receipt throughout your build. The reclaim can be significant - typically £15,000-40,000 on a standard self-build - and is one of the most valuable financial benefits of self-building.
What does the contingency cover and is 15% enough?
The contingency is a reserve fund for the unexpected - ground conditions that require deeper or more complex foundations, material price rises, design changes, contractor issues, weather delays, or anything else that adds cost or time to your build. On a self-build, cost overruns are very common. Even experienced self-builders with tight programmes typically see 10-15% overrun. If you are a first-time self-builder, managing trades directly, or building on a site with any ground risk, 15% is a minimum - some advisers recommend 20%. Never treat the contingency as spare cash to be spent on upgrades mid-build.
Does the saving vs buying always stack up?
The financial case for self-build is strongest in high-value areas where the developer profit margin being captured is large in absolute terms. In lower-value areas - where house prices are relatively low but labour and materials cost roughly the same - the saving can be smaller or even negligible in percentage terms. However, the financial saving is not the only reason people self-build. Many do it to get a home they could not otherwise afford in a location they want, or to achieve a level of specification, energy efficiency, or design quality that simply is not available on the open market at any price.
What are professional fees and why are they so high?
Professional fees on a self-build typically include: architect or designer fees (for drawings, planning application and building control packages), structural engineer, quantity surveyor, topographic survey, ground investigation survey, planning consultant (if needed), party wall surveyor (if applicable), and energy assessor. Fees vary enormously depending on who you appoint and how much of the project they manage. If you appoint an architect on a full-service contract (design through to completion), fees can be 8-15% of build cost. If you use a self-build package company for your structural design and manage trades yourself, professional fees may be lower - but you take on more risk and management time.
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