Calculate tonnage and bags of sharp sand for your project
Sharp sand (also known as grit sand or concreting sand) is one of the most versatile building materials used in UK construction. Whether you are screeding a floor, pointing brickwork, mixing mortar, or preparing a laying course for paving, knowing exactly how much sharp sand to order prevents costly waste and frustrating shortages. Sharp sand has coarser, angular grains compared to building (soft) sand. This makes it ideal for applications where a strong bond or firm compaction is required. The angular particles interlock under pressure, which is why it is the preferred choice for floor screeds, concrete mixes, and paving sub-layers. Density varies by application because the way sharp sand is used affects how tightly it compacts. Floor screeding uses the highest density (1.6 tonnes per cubic metre) because the sand is compacted firmly into place. Brick pointing uses a lower density (1.5 t/m3) because the mortar mix is more open. General mixing applications fall in between at 1.55 t/m3. This calculator accounts for these differences and adds a 10% waste factor, which is standard practice for UK building projects.
To calculate how much sharp sand you need: 1. Enter the area to be covered in square metres. For rectangular areas, multiply length by width. For irregular shapes, break the area into sections and calculate each separately. 2. Enter the depth in millimetres. Common depths include 50mm for floor screeding, 10-15mm for brick pointing, and 25-50mm for a paving laying course. 3. Select the application type. This determines the density used in the calculation: floor screeding (1.6 t/m3), brick pointing (1.5 t/m3), or general mixing for mortar and render (1.55 t/m3). 4. Review the results. The calculator shows the total weight in tonnes, the number of 25kg bags, and the number of 850kg bulk bags (also called dumpy bags). All quantities include a 10% waste factor to account for spillage, compaction, and over-ordering margins. 5. When ordering, round up to the nearest bulk bag for larger projects, or order individual 25kg bags for smaller jobs. UK builders merchants sell sharp sand in both formats.
The sharp sand calculation converts area and depth into volume, then applies density and waste: Volume (m3) = area (m2) x depth (mm) / 1000 Base weight (tonnes) = volume (m3) x density (t/m3) Total weight (tonnes) = base weight x 1.10 (10% waste factor) 25kg bags = ceiling(total weight x 1000 / 25) Bulk bags (850kg) = ceiling(total weight / 0.85) Densities by application: - Floor screeding: 1.6 tonnes per m3 - Brick pointing: 1.5 tonnes per m3 - General mixing (mortar/render): 1.55 tonnes per m3 The 10% waste factor accounts for spillage during mixing, material left in bags, and slight over-measurement. This is standard practice recommended by most UK builders merchants and is built into the calculation automatically.
Inputs: Area: 10 m2, Depth: 50 mm, Application: Floor screeding
Inputs: Area: 5 m2, Depth: 25 mm, Application: Brick pointing
Inputs: Area: 20 m2, Depth: 40 mm, Application: General mixing
Sharp sand is typically sold in 25kg bags (around 2 to 4 pounds each) or 850kg bulk bags (around 35 to 55 pounds each) at UK builders merchants. For large projects over 3 tonnes, loose tipper delivery is usually the cheapest option per tonne. Always store sharp sand on a hard, dry surface and cover it to prevent rain washing out the finer particles. When mixing mortar or screed, the standard ratio is 4 parts sharp sand to 1 part cement for floor screeds, and 3 parts sharp sand to 1 part cement for pointing mortar. Sharp sand from different suppliers may vary slightly in colour, so try to source all your sand from the same batch if a consistent finish matters.