Construction
Material estimates usually go wrong in predictable ways: units get mixed, waste gets forgotten, or material is ordered before the geometry is settled. This category focuses on turning measured dimensions into quantities you can actually order — volume for pours and fills, area for surfaces, and counts for repeated units.
Use the calculators to estimate first, then confirm against site measurements and the supplier's coverage or yield figures.
Browse construction calculators
Concrete, fill & bulk materials
Surfaces & coverings
Grounds & planting
Siding & trim
Which construction calculator do you need?
Estimate concrete for a slab, footing or post hole, including the number of bags or the delivered volume.
Order fill, sand or gravel by volume, and estimate weight when the supplier sells by the tonne.
Work out roofing material or bundles for a pitched roof from the roof area and pitch.
Tile a wall or estimate the paver base and sand volume for a patio, including a waste allowance for cuts and breakage.
Cover a lawn, bed or driveway with mulch, sand or gravel at a chosen depth and estimate the weight.
Measure floor, wall or ceiling area before buying finish materials, or plan board-and-batten siding coverage.
Units and volume conversions
Dimensions rarely arrive in the same unit: lengths are often measured in feet while depth is quoted in inches. Convert everything to one unit before multiplying, then convert the result — cubic feet to cubic yards, for example, by dividing by 27.
Bulk materials are usually sold by volume or weight, and the two are linked by density. Sand, gravel and soil densities vary with moisture and grading, so treat weight estimates as planning figures and confirm with the supplier.
Waste allowance and ordering
Cutting, breakage and spillage mean the theoretical quantity is almost never the quantity to order. A waste allowance of roughly 5–10% covers most work, and repeated small units such as pavers or tiles often need around 10%.
Ordering slightly more is cheaper than a second delivery, but keep the excess manageable: colour batches and storage limits matter for visible surfaces.
Estimating limits to keep in mind
- Bulk material weights are estimates — density changes with moisture and grading.
- Bag yields and coverage rates differ by manufacturer; check the product label rather than relying on a generic figure.
- Plans, local codes and site conditions can require more material or reinforcement than a simple volume estimate suggests.