Sand & Aggregate Calculator
Calculate sharp sand, building sand, ballast and kiln dried sand for any project. Includes cement bag count, mix ratios, delivery options and 2026 UK pricing.
Sharp sand: coarse angular grains. Use for paving beds, floor screeds and concrete. BS EN 12620.
Area = π × (diameter ÷ 2)²
Use if you already know your total area.
Standard paving bed: 40mm. Floor screed: 65mm. Pipe bedding: 100mm.
15% is standard for sand paving beds that compact when wackered.
Sand:cement ratio. A 4:1 paving bed requires 1 bag of cement for every 4 parts sand by volume.
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Sand Types Guide
Choosing the Right Sand
Sharp Sand (Grit Sand) — Structural Applications
Sharp sand has coarse, angular grains that lock together under compaction, making it the only suitable sand for structural applications. Use for paving beds and patios (40mm, 4:1 mix), floor screeds (65mm, 4:1 mix), concrete production (with ballast) and drainage applications.
Never use building sand for paving beds or screeds — its fine rounded grains don't provide the structural integrity required and can cause slabs to sink or rock. Density: ~1.65 t/m³. Standard: BS EN 12620:2002+A1:2008.
Building Sand (Soft Sand) — Mortar & Render
Building sand has fine, rounded grains that give mortar its workability and plasticity. Use for bricklaying mortar (5:1 or 6:1 mix), pointing and repointing, render coats and general masonry work.
Building sand should never be used in concrete or paving beds — it lacks the angularity required for structural applications. Density: ~1.60 t/m³. Standard: BS EN 13139:2002.
Kiln Dried Sand — Block Paving Joints
Kiln dried sand is a very fine, moisture-free sand used exclusively to fill the joints between block paving after the blocks are laid and compacted. It flows into tight joints by gravity and vibration. Applied at approximately 3–4kg per m².
Apply dry, sweep across the surface with a stiff brush and use a plate compactor to vibrate it into the joints. Top up after the first flush of rain as the joints will settle. Never use wet or damp sand in block paving joints.
Mortar Mix Ratios — Reference Guide
3:1 (strong): path edging, engineering brick, below-DPC work. High cement content gives maximum strength and weather resistance.
4:1 (standard): paving beds, general mortar, concrete block. The most common ratio for domestic groundworks.
5:1 (bricklaying): standard bricklaying mortar for above-DPC work. Slightly more flexible than 4:1, reducing the risk of cracking.
6:1 (render / soft brick): rendering coats and softer historic brickwork where a strong mix would cause structural damage. Never use strong mortar on soft or reclaimed brick.
FAQ
Common Questions
Sharp sand has coarse angular grains and is used for structural applications: paving beds, floor screeds, concrete and drainage. Building sand has fine rounded grains and is used for bricklaying mortar, pointing and render. Never substitute one for the other in structural work — using building sand for a paving bed will cause slabs to sink.
A standard 40mm mortar bed (4:1 mix) requires approximately 0.074 tonnes of sharp sand per m² including 15% compaction. For a 20m² patio you need around 1.5 tonnes of sharp sand and 10 bags of cement. Our calculator gives quantities for your specific area and bed depth.
A standard bulk bag holds approximately 800kg of sand — equivalent to 34 × 25kg small bags. Bulk bags are significantly cheaper per tonne than small bags for any project over 0.5 tonnes, but require a vehicle with adequate ground access for delivery.
Kiln dried sand for block paving joints is applied at approximately 3–4kg per m². For a 20m² driveway you need around 60–80kg, typically 3–4 bags of 20kg kiln dried sand. Apply dry and brush into joints after compaction. Top up after the first rainy period.
Standard bricklaying mortar above DPC uses a 5:1 or 6:1 building sand to cement ratio. Below DPC or in exposed conditions, use a stronger 4:1 or 3:1 mix with engineering brick. Never use sharp sand for bricklaying mortar — its coarse grains make the mix unworkable and reduce bond strength.