Gravel consists of loose rock fragments typically 2–75 mm in diameter. It's used for driveways, walkways, drainage, and as a base layer under concrete and pavers.
Types
- Pea gravel: Smooth, rounded, 3/8" — good for walkways and drainage
- Crushed stone: Angular, interlocks — ideal for driveways and bases
- River rock: Smooth, 1–3" — decorative landscaping
- #57 stone: 3/4" crushed — most popular for driveways
Estimating
1 cubic yard covers about 100 sq ft at 3" depth. Weight: ~1.4 tons per cubic yard (varies by type).
Why Angular Gravel Locks Better Than Round
Crushed, angular stone interlocks under compaction and resists shifting under vehicle weight, making it the standard choice for driveway base layers — smooth, rounded pea gravel looks nicer but shifts and displaces under foot or tire traffic, which is why it's typically reserved for decorative paths and drainage rather than load-bearing surfaces.
Base Layer Depth for Driveways
A proper gravel driveway typically needs 8–12 inches of compacted base material in multiple layers (larger stone at the bottom, finer at the top), not a single thin layer — under-depth bases are the leading cause of ruts, potholes, and drainage problems developing within the first few years.