How to Calculate Gravel for a Driveway

Why driveways are built in layers

A gravel driveway that lasts is rarely a single layer of pretty stone. It is usually built from coarser stone at the bottom, which spreads loads and drains water, topped with finer, well-graded stone that compacts into a firm surface. Each layer is spread and compacted before the next goes down.

Step 1: Area and layer depths

Multiply length by width for the area. Then decide the compacted depth of each layer. Residential driveways often total roughly 8–12 in (20–30 cm) of compacted stone, but soft or poorly drained soils may need more, and local practice varies.

Step 2: Allow for compaction

Stone delivered loose occupies more space than the same stone after compaction. Adding 10–20 % to the finished volume is a common allowance for crushed stone. Without it, you end up with a thinner driveway than planned.

Step 3: Convert volume to weight

Quarries often sell by weight. To convert, multiply the volume by the stone's bulk density. A commonly used figure for crushed stone is about 105 lb/ft³ — roughly 1.4 US tons per cubic yard or 1.7 tonnes per cubic metre — but the right figure is the one your supplier uses for their product.

Step 4: Plan deliveries

Ask your supplier how much their truck carries; capacity depends on the vehicle and local weight limits. Ordering by layer lets you compact the base before the next stone arrives. Make sure the delivery route can carry a loaded truck — a soft verge or a weak culvert can be damaged.

Worked example

• Driveway 50 ft × 10 ft = 500 ft².
• Layers: 4 in base + 4 in middle + 2 in top = 10 in (0.833 ft).
• Volume = 500 × 0.833 = 416.7 ft³; +10 % compaction = 458.3 ft³ = 17.0 yd³.
• Weight = 458.3 × 105 lb = 48,125 lb ≈ 24 US tons.

The same driveway in metric

• Driveway 15 m × 3 m = 45 m².
• Layers: 150 mm base + 100 mm middle + 50 mm top = 300 mm (0.30 m).
• Volume = 45 × 0.30 = 13.5 m³; +10 % compaction = 14.85 m³.
• Weight at 1,680 kg/m³ = 24,948 kg ≈ 25 tonnes.

Choosing stone for each layer

Names for aggregates vary by region and supplier, so describe what you need as well as asking for a product name. As a general pattern:

• Base: larger crushed stone that locks together and lets water drain away from the surface.
• Middle (optional on firm ground): medium crushed stone to bridge between base and surface.
• Surface: smaller, angular crushed stone with fines, which compacts into a firm, stable top. Products sold as dense-grade, crusher run or (in the UK) Type 1 sub-base are typical examples.
• Avoid using round stone such as pea gravel as the main driving surface: rounded particles do not lock together and tend to roll and rut under tyres.

Ground preparation, drainage and edging

Remove topsoil and soft material down to firm subsoil before any stone goes in; organic soil compresses and rots, and stone placed on it will sink. On soft or clay soils, a geotextile separation fabric between the subsoil and the base helps stop the two mixing over time.

Water is the main enemy of a gravel driveway. Give the surface a slight crown or cross-fall so rain runs off to the sides rather than pooling in wheel tracks, and make sure it has somewhere to go. Edging — timber, steel, concrete kerbs or a plastic grid — keeps the stone where you put it.

Maintenance and top-ups

Even a well-built driveway loses some stone into the ground and off the edges. Raking stone back into wheel ruts, regrading occasionally and adding a thin top-up layer every few years keeps it firm. Use the gravel calculator with a depth of about 1 in (25 mm) to estimate a top-up.