Honest material calculator

Calculators that tell you what to buy.

Every other calculator gives you a number you can't take to a shop. Nobody sells 14.6 litres of paint, 1.32 cubic metres of concrete or 34.7 square metres of turf — they sell tins, truckloads and pallets. These work out what you actually put in the trolley, what's left over, and when the honest answer is to buy less.

What makes these different

Answers in real purchase units. Bags, tins, pallets, boxes, boards and bundles — the things a supplier will actually sell you.
We'll tell you to buy less. "You already have enough." "Stop — at this volume order a truck, not 94 bags." No supplier's calculator will ever say that.
No prices, ever. A price baked into a calculator is wrong within months. Type in what you were quoted and we'll do the arithmetic instead.
Nothing is hidden. Every number shows its working. No email gate, no signup, no results-after-you-subscribe.
It runs in your browser. Nothing you type leaves your device. The advertising that pays for the page is Google's and sets its own cookies — we explain exactly what that does rather than claiming it collects nothing.
Printable order sheets. Quantities, assumptions and a blank price column. Hand it across the counter.

Start here — measure it

Square footageAny room, including L-shapes and bays — add sections and get sq ft, m² and sq yd at once. Then it points you at what to buy.Front door Cubic yardsVolume for excavations, fill and slabs, in cu yd, m³ and cu ft — plus roughly how many truckloads that is.And truckloads Board feetTimber volume in board feet and cubic metres — and the nominal size you are charged for, which is not the size you measure.Nominal, not actual

Concrete, aggregate and ground

ConcreteSlabs, pads, footings and post holes. Bags or ready-mix, and which one you actually want.Bags or bulk Gravel & aggregateDriveways, paths, sub-base and bedding sand. In tonnes, with compaction built in.Sold by weight AsphaltDriveways and patching, at compacted depth. Plus the reason it has to be laid the day it lands.Tonnage Concrete slabHow thick a slab needs to be for a shed, patio, drive or garage — and the three layers that are not the concrete.Thickness first TopsoilBeds, borders and new lawns — with the British Standard rule that stops you buying topsoil where subsoil belongs.Settles 20% Dirt & fillRaising a level or backfilling. Starts by asking whether the spoil you already have will do the job.Loose vs compacted SandScreeds, mixes, bedding and backfill — and which sand is the wrong sand, which matters more than the quantity.Damp weighs more Paver sandBedding and jointing under block paving. Tells you when the answer is less sand and more base.Capped at 40 mm MulchBeds and borders — with the depth warning no mulch supplier will give you, because deeper is worse and sells more.Deeper is worse FootingsConcrete for trench and pad foundations. Depth is a ground question and building control decide it.They inspect first French drainStone, pipe, membrane and fall — and the wrong stone, which is why most French drains do nothing.Clean stone only

Sub-base and hardcore

Crushed stoneWhich size to ask for. Clean stone and dense-graded stone do opposite jobs, and the wrong one fails a season later.Size matters #57 stoneClean open-graded stone for drains and drainage layers — with measured densities rather than trade guesses.Doesn't compact Crusher runABC, QP, DGA, 3/4 minus — six names, one material. What your yard calls it and how to order it.Sold by the ton Road base depthHow deep the base goes for cars, vans or a lorry — and how many layers that means.Load sets depth Paver baseUnder patios and driveways, to the published minimums. Where the falls belong, and when bags stop making sense.Base, not sand MOT Type 1UK sub-base in tonnes and bulk bags, with the compaction allowance applied once — not twice, as several calculators do.Clause 803

Surfaces and coverings

PaintWalls, ceilings, woodwork and masonry. Which tins to buy, and what you'll have left.Tins, not litres TileFloors, walls and splashbacks, with pattern-aware waste. The one page that tells you to buy more.Boxes Siding & claddingSquares and boxes — plus the corners, channel and trim that aren't in that number.Squares RoofingBundles of shingles, with pitch and waste allowed for — plus the accessories the square count leaves out.Bundles, not squares

Timber, framing and ground cover

DeckingBoards by length, not by area — because which length your yard stocks changes the order by half.Boards Studs & joistsFraming counts, including the off-by-one that sends people back to the yard.Spaces plus one Sod & turfPallets — and why the delivery date matters more than the quantity.Perishable

Setting out and framing

StairsRisers, treads, run and stringer length — checked against the limits an inspector will use.Code checked FencingPosts, rails and pickets, with the gaps spread evenly instead of a sliver at one end.Bays plus one RebarBars, laps and ties for a slab — including the overlap most calculators forget.Laps included Retaining wallBlock counts, and the drainage that is the reason most retaining walls fail. Says where a design becomes necessary.Over 1 m: design Framing timberStuds and the plates — which run the wall length twice, and are a third of the timber most calculators leave out.Plates included JoistsFloor and ceiling counts, doubling at openings — and why the joist size is a span table, not a calculator.Span decides size BalustersSpindle spacing with every gap inside the limit — including the two against the posts.Safety rule

Masonry and sheet materials

BrickSixty to the square metre — and the coordinating size that makes that number right, which most calculators get wrong.Includes the joint BlockTen to the square metre, plus the weight per block that decides whether it is one person's work.Weight matters PaversPattern decides the waste — 45° herringbone cuts every perimeter unit. Most calculators apply a flat 10%.Pattern waste Plywood & OSBSheets, not square feet. A 2.9 m wall needs three sheet-widths whatever the area says.Sketch it CabinetsKitchens, vanities and laundries — sheets from real carcass sizes, with your local board size and the grain direction that costs you a sheet.UK · US · AU DrywallBoards, and the board length that removes a horizontal joint from every wall.Fewer joints InsulationPacks by the coverage on the bag — plus why a small gap costs more performance than the same fraction of thickness.Fit beats spec

Flooring

FlooringLaminate, vinyl, LVT and engineered — packs by the coverage on the pack, and which floor the room can actually take.Subfloor first LaminateThe expansion gap that is not optional, and the run length most systems cap at 8–10 m.It floats Hardwood floorSolid and engineered — plus the week of acclimatisation that decides whether the floor stays flat.Wood moves

Mixes, mortar and finishes

GroutComputed from your tile size, thickness and joint width — because there is no honest single coverage figure, and we show the formula.No average MortarSand and cement derived from the unit and joint, not a rule of thumb per thousand bricks. Every step shown.Derived, not assumed WallpaperRolls from whole drops, with the pattern repeat allowed for — a large repeat can cost a whole drop per roll.Drops, not area RaftersLength from run and pitch, plus the slope area — which is bigger than the building's footprint, and that is the usual roofing error.Trigonometry Wood stainDecking, fencing and sheds. Rough sawn timber drinks twice what planed does, and the second coat needs less than the first.Buy coat by coat

Finishing

CarpetWhich way to run the roll, how much comes off it, and where the seams land.Roll width Skirting & baseboardCounted wall by wall, because skirting cannot be joined invisibly mid-wall.Wall by wall

Check our arithmetic — and everyone else's

There is an error in this category that produces about 20% too much material, always in the seller's favour, and it is easy to check in thirty seconds. Here is the arithmetic in full — including how to test this site with it.

Every standard our figures rest on is set out on its own page, with what it actually says and — where it matters — where the commonly repeated version of it is wrong.

Why there are no prices here

Bake prices into a calculator and it's out of date within months. Worse, the sums stop making sense: a 10 litre tin is often the same price as two 4 litre tins, and a bulk load can cost less than half as many bags — which flips the answer entirely. Only your supplier knows today's price.

So we don't quote prices. We accept them. Type in what you were quoted and we'll total it, work out the cost per square metre, and find the exact point where bulk delivery overtakes bags for your supplier. That answer can't go stale, because it's built from your numbers on the day.

Free, no login, no email. These calculators are funded by the advertising on the page and nothing else — no affiliate links, no lead generation, no commission on anything you buy. That matters, because a tool paid for by the people selling you the materials can never tell you to buy fewer of them.

The honest cost of that independence is that the ads are Google's, and Google sets cookies to serve them. Your measurements never leave your browser; the advertising is a separate thing on the same page, and the privacy page sets out plainly what it does — including the parts we would rather not have.

Coverage figures, densities and bag yields are trade-typical and deliberately cautious, so you don't run short. Where your product states its own figure, use theirs — every calculator lets you override ours. See every figure we use, and where it came from, read why the site works this way, or tell us if one is wrong.