Gravel Calculator
Calculate how much gravel, shingle or decorative chippings you may need — in tonnes, bulk bags and loose tipper loads. Compaction factor included. All delivery options compared.
20mm gravel: ~1.6 t/m³. Most popular for driveways and paths. Good weed suppression at 50mm depth.
Area = π × (diameter ÷ 2)²
Use if you already know your total area from a plan or survey.
Driveways: 50mm. Garden paths: 40mm. Decorative borders: 30–40mm.
10% accounts for settling and ensures you don't run short. Increase to 15% on uneven ground.
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Laying Guide
How to Lay Gravel
Choosing the Right Depth
30–40mm (decorative): adequate for borders and planters where aesthetics matter more than function. At 30mm, determined weeds can push through.
50mm (standard driveway): the industry-standard depth for domestic driveways. Provides good weed suppression and prevents tyres from displacing gravel. Use 20mm angular gravel — it interlocks and stays put better than rounded pea gravel.
75–100mm (heavy use / drainage): required for regular HGV access or drainage applications. At 100mm, loose gravel provides excellent drainage and structural stability.
Weed Membrane — Essential for Longevity
A permeable weed suppressant membrane laid beneath the gravel is one of the most important steps in a gravel installation. Without it, weeds push up through the gravel within the first season and are almost impossible to control without removing the gravel entirely.
Always use a permeable membrane — never plastic sheeting. Plastic prevents drainage and causes water pooling and ice formation in winter. Overlap membrane strips by at least 150mm and secure with ground pins (1 per m²) before laying your edging and gravel.
Edging & Containment
Gravel without edging migrates onto lawns, paths and borders within months. Install steel or plastic edging strips bedded in the sub-base before laying the membrane. For driveways, concrete kerb edging or block edging provides the most permanent containment.
A gravel board or sleeper edging at 50–75mm above ground level stops gravel spilling onto surrounding surfaces. Factor edging into your project before ordering gravel.
SuDS & Drainage Compliance
Loose gravel is naturally permeable and generally satisfies Building Regulations Part H (Sustainable Drainage) requirements without additional measures. Water percolates through the gravel and membrane into the subgrade below.
However, ensure drainage remains within your property boundary. Gravel driveways that sheet-drain directly onto the public highway are technically non-compliant. A simple gravel-filled channel or rubble soakaway at the boundary keeps runoff on-site.
Aggregate density and grading data used in this calculator is calibrated against BS EN 12620:2002+A1:2008 (Aggregates for Concrete) and BS EN 13242:2002+A1:2007 (Aggregates for Unbound Mixtures). Sub-base specifications follow SHW Clause 803 for MOT Type 1.
FAQ
Common Questions
At 50mm depth, 20mm gravel weighs approximately 0.088 tonnes per m² before the compaction allowance. Add 10% for settling and you need about 0.097 tonnes per m². For a 20m² driveway that's around 2 tonnes or 3 bulk bags.
50mm is the standard depth for domestic driveways. This gives good weed suppression and prevents tyres from displacing the gravel. For heavy vehicles or HGV access, increase to 75–100mm. Garden paths can use 40mm.
A standard UK bulk bag holds approximately 800kg (0.8 tonnes) of 20mm gravel, which is about 0.5 m³. Heavier aggregates like crushed granite can weigh closer to 1 tonne per bag in the same volume.
Yes, for all permanent installations. A permeable weed suppressant membrane prevents weeds from pushing up through the gravel. Without it, you'll be fighting weeds within the first season. Never use plastic sheeting — it blocks drainage and causes pooling.
20mm angular gravel (often sold as 20mm clean stone or shingle) is the best choice for driveways. Angular chips interlock when compacted, staying in place under vehicle tyres. Rounded pea gravel is attractive but rolls under tyres and scatters onto surrounding areas. For a stable base, lay angular gravel on a compacted sub-base.
Cotswold Buff has a typical density of 1.4 tonnes per cubic metre. A 1 tonne bag will cover approximately 18 square metres at a decorative depth of 40mm. You can use the calculator above to get precise quantities for your specific dimensions.
We recommend 30-40mm for decorative chippings. This is deep enough to provide good coverage and hide the membrane beneath, without being so deep that you sink into the stone when walking on it.