Sand Calculator UK: Sharp, Building and Kiln-Dried Sand in Tonnes and Bags
Choose your project, enter the measurements, and this sand calculator estimates the tonnes and bags you need. The second tab works as a sand and cement calculator for patio beds, bricklaying, screed and render. The third tab converts tonnes, cubic metres and bags, then shows the coverage of the sand you already have.
More free UK building calculators
Sand is one part of a bigger project. These calculators cover the paving, stone and mortar around it.
Slabs, block paving, sub-base, bedding mortar and patio fall.
MOT Type 1 tonnes, bulk bags, layers and dig-out depth.
Sand, cement and hydrated lime quantities for brickwork, blockwork and repointing.
Cubic metres, bags, cement and ballast for slabs and footings.
MOT Type 1, ballast, sand and gravel in tonnes and bulk bags.
Tonnage, coverage and driveway cost per m².
Bricks per m², mortar and cost for any wall.
Concrete, breeze and aircrete blocks, with mortar and cost.
Why sand orders go wrong
Picture this. A bulk bag of sharp sand arrives for the new block paving driveway, and it looks generous. By the second row of blocks, the bag is empty, and the merchant cannot deliver again until Monday.
Sand is inexpensive, so most homeowners simply estimate by eye. Unfortunately, a laying course compacts by roughly a fifth, and damp sand weighs more than it covers. Choose soft building sand instead of sharp sand, and the paving gradually sinks as well.
Start with the project: the correct sand type, depth and compaction allowance matter more than the area. The calculator applies all three automatically for every project.
How much does 1 tonne of sharp sand cover?
One tonne of sharp sand covers approximately 12.5 m² at 50 mm. Add 25% for a compacted laying course.
How many 25 kg bags of sand do I need?
A tonne of sand fills 40 bags of 25 kg. One 850 kg bulk bag holds the equivalent of 34 small bags.
How to use the sand calculator
Select the tab that matches your question, then complete the form from top to bottom. Each estimate takes about a minute.
- Sand for an area. Choose the project, such as a block paving laying course or a sandpit. The calculator then recommends the sand type, depth and allowance.
- Sand and cement. Choose a patio bed, bricklaying, blockwork, screed or render. Then select a mix between 3:1 and 6:1.
- Tonnes, m³ and bags. Enter any quantity to convert it, and see the area it covers at your chosen depth.
- Enter the area. Add several rectangles for irregular shapes, or use a circle or a known total. Walls use length multiplied by height.
- Add prices if you have them. The calculator then highlights the most economical delivery option, including or excluding VAT.
Every result shows bulk bags, 20 or 25 kg bags and a loose load. You can then order the most practical option for your property.
Sharp sand, building sand or kiln-dried sand?
UK merchants sell several varieties of sand, and each one suits particular jobs. Choosing the wrong sand causes more failures than ordering too little.
| Sand | Also called | Best for | Weight used |
|---|---|---|---|
| Sharp sand | Grit or concreting sand | Laying courses, slab beds, screed and concrete | 1.6 t/m³ |
| Building sand | Soft sand | Bricklaying mortar | 1.6 t/m³ |
| Kiln-dried sand | Jointing sand | Brushing into block paving joints | 1.5 t/m³ |
| Plastering sand | Washed sharp sand | Render and plaster | 1.6 t/m³ |
| Play sand | Silver sand | Sandpits and play areas | 1.5 t/m³ |
| Silica sand | Arena sand | Ménage and sports surfaces | 1.6 t/m³ |
| Granite dust | Grano dust | Under artificial grass | 1.7 t/m³ |
Dry densities used in the calculator. Damp sand weighs up to 20% more.
Sharp sand has coarse, angular grains that interlock and drain freely, as the Heidelberg Materials data sheet describes. Building sand has finer, rounded grains, so the mortar stays workable and smooth. Our honest opinion? Never lay paving on building sand, because it remains mobile and the blocks eventually sink.
How much sand do I need per m²?
These quantities come from the calculator presets, including the usual compaction allowance for each project.
| Job | Sand | Depth | Sand per m² |
|---|---|---|---|
| Block paving laying course | Sharp sand | 30 mm, plus 25% | 60 kg |
| Sand bed under paving slabs | Sharp sand | 40 mm, plus 25% | 80 kg |
| Block paving joints | Kiln-dried sand | 60 mm blocks | 4.4 kg |
| Artificial grass base layer | Sharp sand | 25 mm, plus 25% | 50 kg |
| Sandpit | Play sand | 300 mm, plus 5% | 473 kg |
| Blinding over hardcore | Sharp sand | 25 mm, plus 10% | 44 kg |
| Pipe or cable bedding in a trench | Sharp sand | 100 mm, plus 10% | 176 kg |
| Lawn levelling | Building sand | 5 mm | 8 kg |
| Horse arena or ménage | Silica sand | 100 mm, plus 10% | 176 kg |
Calculated with the tool on this page. Jointing sand includes 10% for topping up.
Laying a complete patio rather than just a sand bed? Our patio and paving calculator adds the slabs, sub-base and jointing. For the crushed stone layer underneath, use our sub-base calculator.
How to calculate how much sand you need
The sand calculation formula is simple. Multiply the area by the depth to find the volume. Next, multiply the volume by the density of the sand, and add any compaction allowance.
Sand coverage by depth
| Depth | Per tonne | Per 850 kg bulk bag | Per 25 kg bag |
|---|---|---|---|
| 10 mm | 62.5 m² | 53.1 m² | 1.56 m² |
| 25 mm | 25.0 m² | 21.3 m² | 0.63 m² |
| 30 mm | 20.8 m² | 17.7 m² | 0.52 m² |
| 40 mm | 15.6 m² | 13.3 m² | 0.39 m² |
| 50 mm | 12.5 m² | 10.6 m² | 0.31 m² |
| 100 mm | 6.3 m² | 5.3 m² | 0.16 m² |
Dry sharp or building sand at 1.6 t/m³, with no compaction allowance.
Sand weight and volume
| Amount | Weight | Volume |
|---|---|---|
| 1 m³ of sand | 1.6 tonnes | 1 m³ |
| 1 tonne | 1,000 kg | 0.63 m³ |
| 850 kg bulk bag | 850 kg | 0.53 m³ |
| 25 kg bag | 25 kg | 0.016 m³ |
| 1 cubic yard | 1.22 tonnes | 0.76 m³ |
| 1 cubic foot | 45 kg | 0.028 m³ |
Damp sand also bulks up by 20–30% in volume. Consequently, a heaped bucket of wet sand contains less than it appears. For this reason, the calculator always works in dry weight.
Sand and cement calculator: how much for each job?
Most builders measure mixes by volume, such as four parts sand to one part cement. Dry ingredients shrink considerably when mixed with water, so every method includes an allowance.
| Job | Mix | Sand per m² | Cement per m² |
|---|---|---|---|
| Patio mortar bed, 40 mm | 4:1 | 68 kg | 15.3 kg |
| Patio mortar bed, 40 mm | 5:1 | 71 kg | 12.8 kg |
| Bricklaying, single skin | 4:1 | 36 kg | 8.1 kg |
| Blockwork, 100 mm blocks | 4:1 | 13.4 kg | 3.0 kg |
| Floor screed, 50 mm | 4:1 | 89 kg | 20.1 kg |
| Render, 20 mm | 5:1 | 39 kg | 7.0 kg |
Beds, screed and render at 1.33 times the volume. Mortar from the joint volume at 1.52 times, as in our mortar calculator.
How much cement for 1 tonne of sand?
| Mix | Cement per tonne of sand | 25 kg bags |
|---|---|---|
| 3:1 (strong) | 300 kg | 12 |
| 4:1 (general) | 225 kg | 9 |
| 5:1 | 180 kg | about 7 |
| 6:1 (lean) | 150 kg | 6 |
Use 4:1 for patio beds, screed and general blockwork. Choose 5:1 for rendering and for most bricklaying above the damp-proof course. Laying a slab shed base on a mortar bed? Use the patio bed option, because the method is identical. For lime mortars and repointing, our mortar calculator covers every designation. Mixing your own concrete with sharp sand and gravel? Our concrete calculator handles that mixture.
Sand calculator examples for UK projects
We calculated each project using the default settings, so you can compare your own figures.
Example 1: block paving driveway
An 8 × 5 m driveway in 200 × 100 × 60 mm blocks
Example 2: porcelain patio
A 5 × 3.6 m patio on a 40 mm mortar bed at 4:1
Example 3: garden wall
10 m² of single-skin brickwork at 4:1
Planning the wall itself? Our step-by-step brick wall guide explains the footing and laying.
Example 4: sandpit
A 2 × 2 m sandpit filled 300 mm deep
Example 5: floor screed
A 5 × 4 m floor screeded 50 mm thick at 4:1
Bulk bags, 25 kg bags or a loose load?
The best way to buy sand depends on the quantity and the access to your property. Enter local prices in the calculator, and it identifies the cheapest option automatically.
| Option | Typical size | Best for | Watch out for |
|---|---|---|---|
| Small bags | 20 or 25 kg | Repairs, pointing and small beds | Costs far more per tonne |
| Bulk bags | 800–1,000 kg | Patios, driveways and walls | A crane lorry needs firm access |
| Loose load | From 4–5 tonnes | Big bases and arenas | It tips where the lorry stops |
Sharp sand bulk bags cost roughly £72–£77 at national merchants in October 2026. Cement costs about £7.50–£8.50 per 25 kg bag.
Store bulk bags on a board and cover them with a tarpaulin. Wet sand weighs more, clumps inside the mixer and alters your mix ratios.
Sand mistakes that cost money
These common errors cause most problems with sinking paving and crumbly mortar.
- Building sand under paving. Soft sand remains mobile, so blocks and slabs gradually sink and become uneven.
- No compaction allowance. A laying course compresses considerably, so order approximately 25% more sand.
- Sharp sand for bricklaying. Coarse grains produce a harsh mortar that is difficult to work.
- Damp sand for jointing. Only dry kiln-dried sand flows completely into narrow block joints.
- Guessing the cement. At 4:1, every tonne of sand requires nine bags of cement.
Mortar sand data sheets, such as the Holcim mortar sand data sheet, list grading limits that suit bricklaying. Ordering gravel or MOT Type 1 as well? Our aggregate calculator covers every type of stone and gravel.
Sand calculator FAQs
How the sand calculator gets its numbers
The calculator multiplies your area by the depth and the compaction allowance. Then it multiplies by the dry density of the sand and rounds up to whole bags.
Sand weighs 1.6 t/m³, kiln-dried sand 1.5 t/m³ and cement 1.44 t/m³. Mortar beds use 1.33 times their volume, and brick mortar uses 1.52 times the joint volume. These figures match our paving and mortar calculators exactly.
Remember that empty bulk bag on the second row of blocks? The correct sand type plus a compaction allowance finishes the driveway in one delivery. Prices checked in October 2026. Treat results as estimates, and confirm the bag weights with your merchant.
What are you using sand for, and did you choose bulk bags or small bags? Tell us through our contact page. Genuine projects help us improve the calculator.