For a standard residential driveway, you typically need a total depth of 100mm to 150mm. This usually consists of a 100mm sub-base layer (like MOT Type 1) and a 50mm top layer of decorative gravel. As a rule of thumb, a double driveway (approx. 50m²) will require around 8 to 10 tonnes of gravel.

To calculate gravel tonnage, first find the volume in cubic meters by multiplying the area (length × width) by the depth. Then, multiply the volume by the density of the gravel. Standard gravel has a density of approximately 1.7 tonnes per cubic meter. Formula: Weight (Tonnes) = Length (m) × Width (m) × Depth (m) × Density (1.7).

A driveway should have a compacted depth of at least 100mm (4 inches) for light vehicles, and up to 150mm (6 inches) for heavier vehicles or poor ground conditions. This is usually laid in two layers: a 100mm compacted sub-base and a 50mm finishing layer of decorative gravel.

Coverage depends on the depth you lay the gravel. Assuming a standard density of 1.7 tonnes/m³: 1 tonne will cover approximately 11.5 square meters at a depth of 50mm (2 inches). At a depth of 100mm (4 inches), 1 tonne will cover approximately 5.8 square meters.

Gravel is a naturally occurring rock fragment formed by weathering and erosion, typically rounded in shape. Aggregate is a broader category that includes gravel, crushed stone, and recycled concrete. In landscaping and construction, ‘aggregate’ often refers to crushed, angular materials (like MOT Type 1) that lock together well for a stable sub-base, while ‘gravel’ refers to the smoother, decorative top layer.

For a driveway top layer, a gravel size of 10mm to 20mm (roughly 0.4 to 0.8 inches) is ideal. Smaller gravel (pea gravel) can get stuck in tire treads and be kicked around, while very large gravel is uncomfortable to walk on and difficult to shovel. A 20mm angular gravel is particularly good as it locks together and resists movement.