River Rock Calculator
Plan your construction materials project with our free river rock calculator. Get precise measurements, material lists, and budgets.
Formula
Tons = (L x W x Depth/12) / 27 x Density
Multiply length (ft) by width (ft) by depth (converted from inches to feet) to get cubic feet. Divide by 27 for cubic yards. Multiply by the rock density (typically 1.4-1.55 tons per cubic yard for river rock) to get tons. Divide total pounds by bag weight for bag count.
Worked Examples
Example 1: Garden Bed Border
Problem: Calculate medium river rock for a 30 ft x 4 ft garden border at 3 inches deep.
Solution: Area = 30 x 4 = 120 sq ft\nVolume = 120 x (3/12) = 30 cu ft = 1.11 cu yd\nTons = 1.11 x 1.45 = 1.61 tons\nBags = ceil(3,220 / 50) = 65 bags
Result: 1.11 cu yd, 1.61 tons, 65 bags (50 lb)
Example 2: Dry Creek Bed
Problem: Calculate large river rock for a 40 ft x 6 ft dry creek bed at 5 inches deep.
Solution: Area = 40 x 6 = 240 sq ft\nVolume = 240 x (5/12) = 100 cu ft = 3.70 cu yd\nTons = 3.70 x 1.50 = 5.56 tons\nTruck loads = 1
Result: 3.70 cu yd, 5.56 tons, 1 truck load
Frequently Asked Questions
How deep should river rock be for landscaping?
River rock depth depends on the stone size and intended use. Small river rock (1 to 2 inches) should be laid 2 to 3 inches deep for garden beds and decorative areas. Medium rock (2 to 4 inches) works best at 3 to 4 inches deep for pathways and borders. Large river rock (4 to 8 inches) needs 4 to 6 inches of depth for drainage areas and dry creek beds. For weed prevention, a minimum of 2 inches is necessary to block light from reaching the soil. Using landscape fabric underneath reduces the required depth and prevents rocks from sinking into the soil.
How much does a ton of river rock cover?
Coverage per ton varies based on the rock size and depth. At 2 inches deep, one ton of small river rock covers approximately 100 to 120 square feet. At 3 inches deep, coverage drops to about 70 to 80 square feet per ton. At 4 inches deep, expect roughly 50 to 60 square feet per ton. Larger stones have more void space between them, so they cover slightly more area per ton at the same depth. These are estimates that can vary 10 to 15 percent based on the specific stone shape, grading, and how tightly the stones pack together.
Should I use landscape fabric under river rock?
Landscape fabric is strongly recommended under river rock for most applications. It prevents weeds from growing up through the rock, stops the rock from sinking into the soil over time, and separates the decorative stone from the native soil. Use a professional-grade woven geotextile fabric, not cheap plastic sheeting which can deteriorate and tear. Overlap fabric seams by at least 6 inches and secure with landscape staples every 2 to 3 feet. The one exception is in drainage applications where you want water to filter through the stone into the ground.
What is the difference between river rock, pea gravel, and crushed stone?
River rock is naturally rounded and smoothed by water erosion, typically 1 to 12 inches in diameter, and comes in earth-tone colors. It is ideal for decorative landscaping, dry creek beds, and areas where a natural look is desired. Pea gravel is very small (1/4 to 3/8 inch) rounded stone that is comfortable to walk on and works well for pathways and play areas. Crushed stone has angular edges from mechanical processing, which allows it to lock together and compact well, making it better for driveways, base material, and areas that need structural stability.
How do I calculate how many bags of river rock I need?
First calculate the total weight needed by determining the area (length times width in feet), multiplying by the depth in feet, dividing by 27 to get cubic yards, then multiplying by the density (about 1.4 to 1.5 tons per cubic yard). Convert tons to pounds (multiply by 2000), then divide by the bag weight (typically 50 pounds). For example, a 10 by 10 foot area at 3 inches deep needs about 0.93 cubic yards, or 1.34 tons, which is 2,680 pounds or 54 bags of 50 pounds each. Bulk delivery is usually more economical for quantities over 1 ton.
How accurate are the results from River Rock Calculator?
All calculations use established mathematical formulas and are performed with high-precision arithmetic. Results are accurate to the precision shown. For critical decisions in finance, medicine, or engineering, always verify results with a qualified professional.