UK Building Calculators for DIY & Construction Projects
Free, practical calculators for UK homeowners, DIYers and tradespeople. Work out quantities for concrete and bases, aggregates, patios, fencing, flooring, walling and waste - quickly and clearly.
All calculators
Pick your material or project type to get started.
Concrete Base Calculator
Work out how much concrete you need for a shed base, garage base or garden room. Bags or ready-mix.
MOT Type 1 Calculator
Calculate MOT Type 1 in tonnes and bulk bags for patios, driveways and sub-bases. Compaction factor included.
Sub Base Calculator
Work out sub-base quantities for any material - MOT Type 1, hardcore, crushed stone or gravel.
Postcrete Calculator
Calculate how many bags of Postcrete you need per fence post, based on hole size and depth.
Fence Post Concrete Calculator
Concrete for fence posts - Postcrete bags, dry-mix or ready-mix. Works for any number of posts.
Patio Slab Calculator
Work out exactly how many patio slabs you need. Accounts for joint gaps, wastage and pack sizes.
Gravel Calculator
Calculate gravel in tonnes and bulk bags for driveways, garden paths and decorative borders.
Aggregate Calculator
Calculate quantities for ballast, sharp sand, MOT Type 1, scalpings and more.
Plasterboard Calculator
Work out how many sheets of plasterboard you need for walls and ceilings, including openings.
Self-Levelling Compound Calculator
Calculate how many bags of floor leveller you need for any area and pour depth.
Floor Screed Calculator
Work out screed quantities in bags, kg and tonnes for sand:cement, anhydrite or rapid-set screed.
Mortar Calculator
Calculate cement bags and sand for brickwork and blockwork. Adjustable mix ratios from 1:3 to 1:6.
Rendering Calculator
Work out how many bags of render you need. Add multiple walls and deduct windows and doors.
Skip Size Calculator
Find out what size skip to hire for your project - garden clearance, kitchen, extension and more.
Sharp Sand Calculator
Calculate sharp sand in tonnes, kg and bags for patios, paving slabs, artificial grass and screeding.
Artificial Grass Sub Base Calculator
Calculate MOT Type 1, sharp sand, grano dust, weed membrane and pins for an artificial grass base.
Fence Panel Calculator
Work out how many fence panels, posts, gravel boards and bags of Postcrete you need for a garden fence.
Soakaway Crate Calculator
Estimate the number of soakaway crates needed for patios, driveways and garden drainage projects.
Choose your project
Browse calculators by project type.
Concrete & bases
Shed bases, garden rooms, garage floors
- Concrete Base Calculator
- Sub Base Calculator
- MOT Type 1 Calculator
Patios & paving
Patio slabs, sub-base, bedding layers
- Patio Slab Calculator
- MOT Type 1 Calculator
- Sub Base Calculator
Fencing & posts
Fence panels, posts, gate posts, concrete mix
- Fence Panel Calculator
- Postcrete Calculator
- Fence Post Concrete Calculator
Aggregates & gravel
Driveways, paths, borders, sharp sand
- Sharp Sand Calculator
- Gravel Calculator
- Aggregate Calculator
- MOT Type 1 Calculator
Flooring
Floor screed, self-levelling compound
- Floor Screed Calculator
- Self-Levelling Compound Calculator
Brickwork & rendering
Mortar, render, brickwork quantities
- Mortar Calculator
- Rendering Calculator
Plasterboard
Rooms, ceilings, stud walls
- Plasterboard Calculator
Waste & skips
Skip size guide for any project
- Skip Size Calculator
Garden & groundworks
Artificial grass, fencing and drainage
- Sharp Sand Calculator
- Artificial Grass Sub Base Calculator
- Fence Panel Calculator
- Soakaway Crate Calculator
What can you work out?
These calculators help you plan material quantities for common UK home improvement projects.
Concrete
- Volume in m³
- Bag count (20kg or 25kg)
- Ready-mix quantity
- Shed, garage and garden room bases
MOT Type 1 & Sub-base
- Tonnes ordered
- Compaction factor applied
- Bulk bags and 25kg bags
- Patios, driveways and paths
Patio slabs
- Number of slabs needed
- Wastage for cuts
- Pack count
- Any slab size or joint gap
Postcrete & fence posts
- Bags per post
- Total bags
- Hole volume
- Any number of posts
Flooring
- Floor screed bags and tonnes
- Self-levelling compound bags
- Sand:cement and anhydrite screed
- Adjustable depth and coverage
Mortar & render
- Cement bags and sand
- Adjustable mix ratios
- Render bags for any wall area
- Openings deducted automatically
Gravel & aggregate
- Tonnes required
- Bulk bags needed
- Small bag count
- Multiple material types
Plasterboard & waste
- Total board count
- Openings deducted
- Skip size guide
- Any project type
Practical tools for homeowners, DIYers and tradespeople
I built Build Calculators because I kept running into the same problem: planning a patio, a shed base or fence posts and spending ages trying to work out how much material to order. Forums gave conflicting advice. Supplier websites buried their calculators or made them too complicated.
The worst moment was ordering MOT Type 1 for a patio sub-base without accounting for compaction. I ordered for the loose depth rather than the compacted depth I needed - and had to wait three days for another delivery. That mistake is what these calculators exist to prevent.
Whether you are a homeowner planning a first patio, an experienced DIYer pricing up materials, or a tradesperson doing a quick quantity check on site - these calculators give you a solid starting point. Practical, honest about their assumptions, and built for real UK projects.
Frequently asked questions
Are these calculators suitable for UK projects?
Yes - all the calculators are built specifically for UK DIY and construction projects. We use metric measurements, UK bag sizes (20kg and 25kg), bulk bag estimates based on UK suppliers, and material densities common in the UK market.
How accurate are the results?
The calculators give reasonable planning estimates for typical projects. They are not guaranteed to be exact - actual quantities depend on site conditions, material variation, supplier product specifications and how the work is carried out. Always allow for some wastage and get a quote from your supplier before ordering.
Do I need to be a professional to use these?
Not at all. These calculators work for homeowners tackling a first project, experienced DIYers who do this regularly, and tradespeople who want a quick quantity check without getting a calculator out. They give you a useful starting point so you can estimate costs and order sensibly.
Why do MOT Type 1 and sub-base calculators include a compaction factor?
Loose aggregate compacts significantly when rolled or plate-compacted. If you order by the loose volume, you will not have enough material once it settles. Our calculators account for this - you enter the compacted depth you need, and we work back to how much loose material to order.
What is a bulk bag?
A bulk bag (also called a tonne bag or jumbo bag) is a large polypropylene sack typically holding around 800–900kg of aggregate. They are a common way to buy MOT Type 1, gravel, sand and other aggregates in the UK. Our calculators estimate how many bulk bags you need alongside tonnes and small bags.
Can I use these calculators for commercial or structural projects?
These calculators are for planning and estimation on everyday DIY and home improvement projects. For commercial, structural or safety-critical work, always consult a qualified professional or structural engineer. Our results are not a substitute for professional advice.
Planning estimates only
These results are estimates for planning purposes only. Actual material quantities can vary based on site conditions, compaction, wastage, product size, installation method and supplier guidance. For structural, safety-critical or regulated work, always consult a qualified professional.