How Much Rock or Gravel Do You Need?
Calculate cubic yards and tons of landscaping rock, gravel, or decorative stone by area and depth.
Calculating Rock Quantities
Cubic yards = (Length × Width × Depth in inches ÷ 12) ÷ 27. Then convert to tons using the rock density. A 20×10 ft area at 3" deep needs 0.56 cubic yards ≈ 0.8 tons of pea gravel. Common depths: 2" for decorative ground cover, 3" for weed suppression, 4" for driveways and high-traffic areas. Always order 10% extra for settling and fill.
Choosing the Right Rock
Pea gravel: 3/8" rounded — walkways, patios, drainage. River rock: 1-3" smooth — decorative beds, dry creek beds. Crushed granite: Angular, compacts well — driveways, paths. Lava rock: Lightweight, porous — mulch alternative, fire pits. Pro tip: Place landscape fabric under all rock installations — without it, rocks sink into soil within 1-2 years, requiring expensive re-installation.
The most common rock landscaping mistake: not using landscape fabric. Without it, rocks sink into the soil within 1-2 seasons, weeds grow through, and you end up re-doing the entire project. Commercial-grade landscape fabric (not the cheap $0.10/ft stuff) costs $0.30-0.50/ft and prevents this problem for 10-15 years.
