Calculators
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Plasterboard
Plasterboard calculator
Room size, walls and ceiling, board size and waste allowance → sheets, screws and scrim tape.
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Paint
Paint calculator
Wall area or full room dimensions, coats and coverage → litres needed, and which tins to buy.
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Turf
Turf calculator
Lawn length and width, roll size and cutting allowance → rolls of turf, plus topsoil if you need it.
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Paving
Paving calculator
Patio size, slab size and joint width → slabs, MOT Type 1 sub-base and sharp sand bedding.
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Concrete
Concrete calculator
Slab or footing dimensions and depth → cubic metres, plus cement, sand and aggregate by the bag, or ready-mix.
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Gravel
Gravel calculator
Area, depth and gravel type → tonnes, plus 850 kg bulk bags or 25 kg bags.
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Topsoil
Topsoil calculator
Bed or border size, depth and settlement allowance → tonnes of screened topsoil and bulk bags.
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Decking
Decking calculator
Deck size, board width and joist centres → boards, joists, screws and hangers.
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Fence
Fence calculator
Fence run, post centres and panel width → posts, panels, gravel boards and bags of postcrete.
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Flooring
Flooring calculator
Room area, pack coverage and waste → packs of flooring, underlay and scotia.
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Brick
Brick calculator
Wall area, brick size and joint width → bricks, blocks, mortar, sand and cement.
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Worktop
Kitchen worktop calculator
Run lengths, depth and joint type → worktop lengths, mitre allowance, upstand and cost.
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Carpet
Carpet and rug calculator
Room size and roll width → carpet length, underlay, gripper, door bars, and the rug size that fits.
Why bother calculating?
Almost every DIY material is sold in a fixed unit: whole plasterboard sheets, whole tins of paint, whole turf rolls, whole paving slabs, and concrete by the cubic metre. You cannot buy 0.37 of a slab, and a merchant will not sell you 380 g of cement.
That means the useful answer is never just an area. It is a purchasing answer — how many boards, how many tins of which size, how many tonnes of sub-base. That is what these calculators give you: a rounded-up quantity, the arithmetic behind it, and a shopping list you can read out at the trade counter.
Everything is worked out the way a tradesperson would on site, using the module sizes merchants actually stock, and with a waste allowance for cuts and breakages. Where an allowance is an industry rule of thumb rather than an exact figure, we say so on the page instead of hiding it in a black box.
How the calculators handle your numbers
All measurements are metric, because that is how UK materials are sold: metres and centimetres for dimensions, millimetres for board, slab and joint sizes, kilogrammes and tonnes for bagged materials, and litres for liquids. You can type a plain number — 2.4 — and the box will assume the unit in its label. If you prefer, type the unit yourself: 2400mm, 2.4m or 240cm all work in the same box.
Blank, zero, negative and non-numeric entries are caught with a plain-English message rather than a nonsense result. Quantities are always rounded up for real purchasing, and the working is shown underneath each result so you can check it or adjust it for your own job.
Is anything sent anywhere?
No. These pages are plain HTML, CSS and JavaScript with no frameworks, no fonts loaded from third parties and no analytics. The calculation happens in your browser, which also means the pages work offline — handy when you are standing in a yard with no signal.
Before you order
Allowances are deliberately slightly generous, because a spare bag of sand is cheaper than a wasted afternoon. Treat the figures as a planning estimate rather than a quote: check your own measurements twice, confirm what your merchant actually stocks, and buy the extra tin or the extra slab while you are there.
If a calculator asks for a number you do not know — coverage per litre on a tin, or sub-base depth for a driveway — the SEO notes under each tool explain the usual UK figures and when to go deeper.