Plan your project. Order the right amount.
Estimate materials, waste, weight and cost for decking, gravel, concrete, patios, brickwork and more. Built for the UK and the US, with every formula shown.
1. Where are you?
United Kingdom: prices in GBP, VAT, and paving slabs, timber and MOT Type 1 sub-base named the way your merchant does.
2. What are you building?
Count decking boards by row rather than by area, plan the cuts, and size the joists, bearers, posts, fixings and post-hole concrete.
All calculators
Six complete estimators. Each one shows its formulas, assumptions and rounding.
Decking calculator
Count decking boards by row rather than by area, plan the cuts, and size the joists, bearers, posts, fixings and post-hole concrete.
Open calculator →
Gravel calculator
Work out gravel, chippings and sub-base quantities by volume, weight, bags, bulk bags or tonnes — including the compaction allowance most calculators leave out.
Open calculator →
Concrete slab calculator
Calculate concrete volume, bag counts, ready-mix orders, sub-base and mesh for slabs, bases and pads in cubic metres or cubic yards.
Open calculator →
Topsoil calculator
Estimate topsoil for lawns, borders and raised beds in litres, cubic metres or cubic yards — with the settlement allowance that stops beds sinking.
Open calculator →
Patio and paving calculator
Count slabs or pavers including joint widths, then size the sub-base, bedding mortar, jointing compound and edge restraints for the whole build-up.
Open calculator →
Brick wall calculator
Count bricks or blocks from the co-ordinating size, deduct openings, and size the mortar, sand, cement and wall ties for single skin, solid and cavity walls.
Open calculator →
What a breakdown looks like
A 20 m² patio in 600 × 600 mm slabs, laid on a full mortar bed over 100 mm of compacted sub-base. Every line shows how it was rounded.
Example materials list
10% waste includedPlus approximately 6.8 tonnes total weight, a delivery assessment, an SVG layout diagram and a printable shopping list.
How estimates work
- 1Everything runs in one set of base unitsMetres, square metres, cubic metres and kilograms. Your input is converted once at the start and once at the end, so nothing drifts between systems.
- 2Waste is added before purchase roundingYou cannot buy 30.14 boards. The waste allowance is applied to the theoretical quantity, and only then is it rounded up to a whole purchase unit.
- 3Quantities become real purchase unitsBags, bulk bags, tonnes, cubic yards, packs and pallets — sized to how suppliers in your region actually sell.
- 4Every number shows its workingThe formula, the assumptions, the density range, the rounding rule and the source. If a figure looks wrong you can check it rather than guess.
28
Documented assumptions
Every density, bag yield and coverage rate carries a value, a range, a source and a review date. Last reviewed 2026-07-01.
See the data →No invented prices
Costs come from you
This site does not scrape or estimate supplier prices. Totals appear only from prices you enter, and the wording never implies otherwise.
Corrections welcome
Wrong answers are bugs
If a calculator disagrees with your merchant, tell us. Reports are checked against the published sources and fixed.
Report an error →Material guides
The reference material behind the calculators — depths, densities, coverage rates and waste allowances.
Decking
Board counts, gaps, cutting plans and the frame beneath — for timber and composite decks.
Gravel and aggregates
Volumes, densities, depths and the compaction allowance that decides whether your sub-base order is right.
Concrete
Slab volumes, bag yields, ready-mix ordering and the thickness that suits the job.
Topsoil
Depths for lawns and beds, settlement allowances, and what a bulk bag holds.
Patios and paving
Slab counts including joints, sub-base depth, bedding mortar and jointing.
Brickwork
Brick and block coverage, standard sizes, mortar quantities and wall areas.