River Rock Calculator: Free Online River Rock Estimator

Use our free river rock calculator to determine exactly how much river rock you need by volume and weight for your landscaping, dry creek bed, or drainage project. Designed for landscapers, garden designers, and DIY homeowners, this tool calculates the cubic yards and tons of river rock required based on your area dimensions. Enter your length, width, depth, and density to get instant, accurate results for ordering.

How to use this calculator.

1. Measure your project area. Measure the length and width of the area to be covered in feet. For winding dry creek beds, measure the centerline length and average width in sections.
2. Select the rock depth. For decorative ground cover, use 2 inches. For dry creek beds and drainage swales, use 3-4 inches. River rock larger than 2 inches in diameter needs deeper coverage for full ground concealment.
3. Adjust the density. The default density is 95 lb/ft³ for mixed-size river rock. Larger rocks (3-6 inches) leave more air gaps and have lower bulk density. Smaller graded rock packs tighter.
4. Review your results. The calculator shows volume in cubic yards and weight in tons. Landscape supply yards typically sell river rock by the ton or by the cubic yard.

How do you calculate river rock volume and weight?

River rock volume and weight follow the same area-times-depth formula as other bulk aggregates.

Volume (cu yd) = Length (ft) × Width (ft) × Depth (in) ÷ 324

Weight (tons) = Volume (cu yd) × Density (lb/ft³) × 27 ÷ 2,000

Where:

• 95 lb/ft³ is the typical bulk density of river rock, slightly lighter than crushed stone (100 lb/ft³) due to rounded shapes creating more air voids.
• 2,565 lb is the approximate weight of one cubic yard of river rock (1.28 tons).
• River rock is naturally rounded by water action. Common sizes range from 3/4 inch to 6 inches in diameter.

Example calculation.

Let's calculate the river rock needed for a dry creek bed.

Scenario: You are creating a dry creek bed that is 25 ft long and 3 ft wide with 3 inches of 2-4 inch river rock at 95 lb/ft³.

1. Calculate the volume: 25 ft × 3 ft × 3 in ÷ 324 = 0.69 cu yd
2. Calculate the weight: 0.69 cu yd × 95 lb/ft³ × 27 ÷ 2,000 = 0.89 tons

Result: You need approximately 0.75 cubic yardsor about 1 ton of river rock for this dry creek bed. River rock typically costs $120-$180 per ton depending on size and regional availability.

Tips from the field.

• Use different sizes for a natural look. Mix 2-3 different sizes of river rock (e.g., 1-2 inch, 2-4 inch, and 4-6 inch) for the most natural-looking dry creek bed. Uniform-sized rock looks artificial. Place larger rocks as focal points.
• Install landscape fabric. Place heavy-duty woven landscape fabric under all river rock areas. River rock is heavy and permanent -- once it sinks into soil, it is extremely difficult to remove. The fabric also prevents weed growth.
• Dig a shallow trench for creek beds. For dry creek beds, excavate 4-6 inches below grade first, then fill with river rock. This creates a natural channel shape and prevents rock from spreading onto adjacent lawn.
• Do not use river rock near trees. A thick layer of river rock over tree roots can compact the soil and restrict water and oxygen to the roots, slowly killing the tree. Use mulch or thin ground cover near trees instead.

Disclaimer: This calculator provides estimates for planning purposes only. Actual material requirements vary based on rock size distribution, installation method, and surface irregularities. River rock weight varies by stone type (granite, basalt, limestone) and moisture content. PavementCalculator.com assumes no liability for material overages or shortages.