Rock Calculator

How to Calculate Landscape Rock Needed?

Multiply the area length by the width to get square footage. Multiply the square footage by the depth in feet to get cubic feet. Divide by 27 for cubic yards. A landscape bed 15 x 10 feet at 3 inches deep needs 15 x 10 x 0.25 = 37.5 cubic feet = 1.39 cubic yards. Multiply by the rock density to find the weight. River rock at 2,600 lbs/yd3 gives 1.39 x 2,600 = 3,614 lbs or 1.81 tons. The calculator above handles these conversions for river rock, crushed rock, lava rock, and decorative stone.

What Types of Landscape Rock Are Available?

River rock consists of smooth, rounded stones in sizes from 1 to 6 inches, formed naturally by water erosion. It works well for dry creek beds, drainage channels, and decorative borders. Crushed rock is angular stone broken mechanically, available from 1/4-inch screenings up to 4-inch pieces. It compacts well and is used for pathways and structural fill. Lava rock is lightweight volcanic stone in red, brown, or black, popular as decorative mulch because it does not decompose. Decorative stone includes polished pebbles, tumbled glass, and specialty materials used in accent areas, water features, and Zen gardens. Each type has a different density and coverage rate per ton.

How Deep Should Landscape Rock Be?

For ground cover and mulch replacement: 2-3 inches of small rock (1-2 inch size). For pathways: 3-4 inches of crushed rock or decomposed granite. For dry creek beds: 4-6 inches of river rock. For drainage areas: 6-12 inches of washed gravel. For decorative accent areas: 2-3 inches of polished or tumbled stone. Using larger rocks (3-6 inch) requires less depth because each stone covers more vertical space. Smaller rocks (under 1 inch) need more depth because they settle and shift more. In all cases, lay landscape fabric underneath to prevent weed growth through the rock layer.

How Much Does Landscape Rock Weigh?

Weight varies significantly by type. River rock: 2,600 lbs per cubic yard. Crushed rock: 2,800 lbs. Lava rock: 2,400 lbs (lighter due to air pockets in the volcanic stone). Decorative lightweight stone: 1,500 lbs. Flagstone: approximately 3,000 lbs per cubic yard. Weight determines delivery logistics. A standard tandem dump truck carries 10-14 cubic yards by volume but is limited to roughly 20-22 tons by weight. For heavy materials like crushed rock, the weight limit may be reached before the truck bed is full. Tell the supplier what material you are ordering so they load the truck correctly.

How Much Does Landscape Rock Cost?

Bulk pricing: standard river rock costs $40-$80 per ton. Crushed stone runs $25-$50 per ton. Lava rock costs $50-$100 per ton. Mexican beach pebbles and premium decorative stones range from $100-$400 per ton. Delivery adds $50-$150 per truckload. Bagged rock at home centers costs $5-$10 per 50-pound bag, which works out to $200-$400 per ton. Bulk delivery is dramatically cheaper for projects needing more than a few hundred pounds. A one-ton delivery covers approximately 100 square feet at 3 inches deep, depending on rock type and density.

Rock vs Mulch: Pros and Cons

Rock does not decompose, does not need annual replacement, does not blow away in wind, and does not attract termites. It works well in low-water xeriscape designs and fire-prone areas where organic mulch creates fuel. However, rock absorbs and radiates heat, raising soil temperature around plants. It does not add nutrients to the soil as it breaks down (because it does not break down). Rock is difficult to remove once installed and makes future planting changes harder. Mulch insulates soil better in both heat and cold, feeds the soil as it decomposes, and is easier to work in for planting changes. The best choice depends on your climate, plants, and maintenance preferences.

How to Install Landscape Rock?

Remove existing mulch, weeds, and debris. Edge the bed with steel, plastic, or stone edging to contain the rock. Lay commercial-grade landscape fabric, overlapping seams by 6 inches and securing with landscape staples. Cut X-shaped slits in the fabric around existing plants. Spread rock evenly to the desired depth using a wheelbarrow and garden rake. Avoid piling rock against plant stems or tree trunks, which traps moisture and promotes rot. For slopes, use angular crushed rock rather than rounded river rock, as the angular pieces interlock and resist washing downhill during rain.

How Many Square Feet Does One Ton of Rock Cover?

Coverage depends on rock density and depth. At 2 inches deep: river rock covers approximately 120 sq ft per ton. At 3 inches: 80 sq ft per ton. At 4 inches: 60 sq ft per ton. Lighter lava rock covers more area per ton because it weighs less per cubic yard: approximately 130 sq ft per ton at 2 inches. Heavier crushed stone covers less: approximately 110 sq ft per ton at 2 inches. These coverage figures help you estimate how many tons to order before the delivery truck arrives. Order 5-10% extra because uneven terrain and settling consume more material than a flat surface calculation suggests.

Frequently asked questions