How Much Gravel You Need
Gravel is sold by volume or by weight, and the calculation starts the same way as any other loose material:
Cubic feet = Area (sq ft) × Depth (inches) ÷ 12
Cubic yards = Cubic feet ÷ 27 Tons ≈ Cubic yards × 1.4
The conversion to weight depends on the stone. Most crushed gravel runs about 1.4 tons per cubic yard, but it varies from roughly 1.1 for light lava rock to 1.7 for dense crushed granite. If your supplier quotes by the ton, ask for their conversion factor rather than assuming.
How Deep
| Application | Depth | Notes |
|---|---|---|
| Garden path, foot traffic | 2–3 in | Over a compacted, weed-suppressed base |
| Walkway | 3–4 in | Edging keeps it in place |
| Patio base under pavers | 4–6 in | Compacted crushed stone, then sand |
| Driveway, cars | 6–8 in total | In two or three compacted layers |
| Driveway, heavy vehicles | 8–12 in total | Larger stone at the base |
| French drain | 12+ in | Clean washed stone, no fines |
A driveway is built in layers, not in one pour: a coarse base course of 2–3 inch stone, a middle course of crushed stone, and a top course of smaller angular gravel. Each layer is compacted before the next. A single deep layer of one size will rut.
Coverage per Ton and per Cubic Yard
| Depth | Area per cubic yard | Area per ton |
|---|---|---|
| 1 inch | 324 sq ft | ~240 sq ft |
| 2 inches | 162 sq ft | ~120 sq ft |
| 3 inches | 108 sq ft | ~80 sq ft |
| 4 inches | 81 sq ft | ~60 sq ft |
| 6 inches | 54 sq ft | ~40 sq ft |
Types of Gravel
| Type | Size | Best for |
|---|---|---|
| Crusher run (road base) | Dust to 1½″ | Base layers — the fines lock it together when compacted |
| #57 stone | ¾″ | Drainage, driveways, under concrete |
| #8 pea gravel | ⅜″ | Paths, playgrounds, decorative beds |
| #4 stone | 1½–2½″ | Driveway base, erosion control |
| Decomposed granite | Fines to ¼″ | Paths that compact to a firm surface |
| River rock | ¾–5″ | Decorative only — rounded stone rolls underfoot |
The key distinction is angular versus rounded. Angular crushed stone interlocks and stays put; rounded river rock does not compact and will migrate under traffic. For any surface that carries weight, use angular stone.
Approximate Weights
| Material | Tons per cubic yard | lb per cubic foot |
|---|---|---|
| Pea gravel | 1.3–1.4 | 96–104 |
| Crushed stone | 1.4–1.5 | 104–111 |
| Crusher run | 1.5–1.6 | 111–119 |
| River rock | 1.3–1.4 | 96–104 |
| Sand | 1.3–1.5 | 96–111 |
| Lava rock | 0.5–0.8 | 37–59 |
These are dry weights. Wet material can be 10–20% heavier, which matters when a truck's payload is the limit.
Preparation Matters More Than Depth
- Excavate to firm subgrade. Gravel laid on soft topsoil will sink into it, however deep the layer.
- Use geotextile fabric between soil and stone. It stops the two mixing, which is the main reason gravel driveways need topping up.
- Compact each layer. A plate compactor over 3–4 inch lifts produces a surface that lasts years rather than months.
- Crown the surface. A driveway should be about 2% higher in the middle so water runs off rather than sitting.
- Edge it. Without edging, gravel migrates outward and the middle thins.
Frequently Asked Questions
How many tons in a cubic yard of gravel?
About 1.4 for typical crushed stone. Ask your supplier for their figure, since it varies by 20% between materials.
How much gravel for a 20 × 20 ft driveway?
400 sq ft at 6 inches is 200 cubic feet, or about 7.4 cubic yards — roughly 10 tons.
Should I use fabric underneath?
Yes for anything carrying traffic. Geotextile separation fabric roughly doubles the life of a gravel driveway for a small fraction of the cost.
How much does a truckload hold?
A standard dump truck carries 10–14 cubic yards. A half-ton pickup should carry no more than about half a yard of gravel, which is already close to its payload limit.