Gravel Driveway: Depth, Base and How Much Gravel

A gravel drive is one of the cheapest hard surfaces you can lay, and you can do it yourself. The mistake that ruins them is treating gravel as a single layer dumped on soil - it needs a proper base, or it rutts and sinks.

The layers (this is what matters)

A driveway that takes vehicle weight is built in two layers over the soil:

1. Sub-base - 100–150 mm (4–6 in) of compacted crushed hardcore (MOT Type 1, or crushed concrete). This is the structural layer that spreads the load.
2. Gravel top layer - 50–100 mm (2–4 in) of your decorative or angular driveway gravel.

So your total dig-out is around 200–250 mm (8–10 in). A purely decorative gravel area or a path can skip the heavy base and use a thinner 40–50 mm layer over a weed membrane.

How much to order

Each layer is area times depth:

volume = length × width × depth

Calculate the sub-base and the gravel separately - they are different depths and different materials. In the gravel calculator, add one area for the gravel layer and another for the sub-base, and it totals each.

Worked example

A 10 m × 3 m driveway with a 100 mm gravel top layer:

1. Area: 10 × 3 = 30 m².
2. Gravel volume: 30 × 0.10 = 3 m³.
3. At roughly 1.5 tonnes per m³, that is about 4.5 tonnes of gravel - plus the sub-base underneath, calculated the same way at its own depth.

Practical tips

• Edge it. Without an edging (timber, brick or metal) the gravel migrates onto the lawn and road. Budget for restraint along both sides.
• Use a membrane between sub-base and gravel to stop weeds and stop the layers mixing.
• Angular gravel locks together and stays put on a slope far better than rounded pea gravel, which scatters underfoot.
• Order by weight. Bulk gravel is sold by the tonne, so convert the volume the calculator gives you using the supplier’s weight per cubic yard or tonne, and order a little generous - it settles.

Spreading gravel as a thin decorative layer rather than building a drive? Set the depth to 40–50 mm in the calculator. Doing beds or borders at the same time? See how much mulch do I need.