Use this free building materials calculator to estimate quantities for common trade and DIY jobs, bricks and blocks, mortar and render, concrete, screed, sub base and aggregates, paving, decking, fencing, plasterboard, roof tiles and slates, and turf and topsoil. Enter your measurements and the estimate updates instantly, with a waste allowance built in.
Building Materials Calculator
Quick, no nonsense quantity estimates for common trade and DIY jobs. Pick a material, enter your measurements, and get an instant estimate with a waste allowance built in.
Based on 60 standard bricks or 10 blocks per m². Deduct openings (doors/windows) from your wall area for a tighter figure. For mortar, use the Mortar & render tab.
Bricklaying assumes ~1 tonne building sand + ~5×25kg cement bags per 1,000 bricks (approx. 1:5, 6). Rendering uses ~300kg cement per m³ of mortar. Ratios vary by mix and joint, confirm before ordering.
Figures are for a general purpose mix (approx. C20, ~1:5 all in ballast: ~2.0 t ballast and ~320kg cement per m³). For anything structural, confirm the mix design. On larger pours, ready mix by the m³ is usually cheaper and easier.
Sand & cement floor screed at approx. 1:4 (~350kg cement per m³). Minimum ~40mm bonded / 50mm unbonded is typical, check your spec.
Tonnage uses typical compacted densities (MOT Type 1 ~2.1 t/m³). Bulk bags counted at ~850kg each. Order a little over for compaction and settlement.
Slab count includes your waste allowance for cuts and breakages. You'll also need bedding mortar, roughly 1 tonne of sharp sand + 6×25kg cement per ~20 m² at 40mm.
Assumes a 5mm gap between boards and joists at 400mm centres. Add a little extra for a diagonal or picture frame layout.
Posts = panels + 1. Postcrete estimated at 2×20kg bags per post, allow more for tall or exposed fences. Gravel boards are one per panel bay.
Add the wall or ceiling areas you're boarding; the tool adds your waste allowance. Standard boards are 2.4 × 1.2 m (2.88 m²).
Coverage and batten gauge vary significantly by manufacturer and pitch, treat this as a ballpark and confirm against the product datasheet before ordering.
Turf rolls are counted at 1 m² each. Topsoil tonnage assumes ~1.5 t/m³. Order turf for same day laying where possible.
Running a builders merchant? OptiFlow answers product and quantity questions like these for your trade customers automatically, 24/7, on top of your existing systems.
See OptiFlow Merchant →Estimates only, always confirm quantities with your merchant before ordering. Figures include your selected waste allowance.
What the calculator covers
Eleven material calculators in one tool: bricks and blocks (60 bricks or 10 blocks per m²), mortar and render, concrete and screed, MOT Type 1 sub base and aggregates by the tonne, paving slabs, timber decking, fencing, plasterboard, roof tiles and slates, and turf and topsoil. Every result includes an adjustable waste allowance for cuts, breakages and compaction.
How the estimates are worked out
The dimensional maths, wall areas, volumes, slab and board counts and aggregate tonnages, use standard industry figures such as 60 bricks per m² and a compacted MOT Type 1 density of about 2.1 tonnes per m³. Mortar and concrete mix figures are conservative rules of thumb that vary with the mix and the joint, so treat them as a guide and confirm before ordering. These are planning estimates to help you scope and price a job, always confirm final quantities with your merchant.
Running a builders merchant? See how OptiFlow Merchant answers product and quantity questions like these for your trade customers automatically, or read our data report on the always on trade counter.