River Rock Calculator
Estimate the volume in cubic yards and total weight in tons of decorative river rock required for gardens, dry creek beds, or landscaping borders.
Calculation Results
Total cubic yards of river rock needed, including waste.
Total weight of river rock needed in short tons (2,000 lbs).
How This Calculator Works
To use the River Rock Calculator:
- Enter the length and width of the decorative garden zone or creek bed.
- Specify the depth of the rock layer (typically 3 inches is recommended to completely hide the soil/landscape fabric below).
- Specify the material density (1.3 tons/cu yd is the standard average for rounded river stone).
- Add a waste allowance. 10% is standard to cover edge shaping and minor depth variations.
Formula & Calculations
River rock volume is calculated based on coverage area and depth, converted to cubic yards and including a waste factor:
Volume (Cubic Yards) = ((Length × Width × Depth) / 27) × (1 + Waste / 100)
Weight is calculated by multiplying the cubic yard volume by the density of the river rocks (tons per cubic yard):
Weight (Tons) = Volume (Cubic Yards) × Density
For standard rounded river rocks, the industry average density is approximately 1.3 tons per cubic yard (which is slightly lighter than angular crushed stone because rounded stones leave larger air voids).
Step-by-Step Calculation Examples
Garden Decorative Bed
A decorative garden border zone measuring 20ft by 10ft wide, filled with a 3-inch layer of river rock at standard density (1.3 tons/cu yd) and 10% waste.
- length: 20
- width: 10
- depth: 3
- density: 1.3
- waste: 10
- volume_cu_yd: 2.04 cu yd
- tons_needed: 2.65 tons
Frequently Asked Questions
How much does a cubic yard of river rock weigh?
A cubic yard of rounded river rock typically weighs between 2,500 and 2,700 pounds, which is approximately 1.25 to 1.35 tons.
What depth should decorative river rocks be laid?
For small-to-medium river rocks (1 to 2 inches in size), a depth of 3 inches is recommended. Laying it shallower will expose the landscape fabric underneath, while laying it deeper than 4 inches makes walking difficult and adds unnecessary expense.
Should I lay landscape fabric under river rocks?
Yes, heavy-duty landscape fabric is highly recommended under decorative river rocks. It prevents the heavy stones from sinking into the dirt over time, blocks weed growth, and allows water to drain into the soil.
What is the difference between river rock and pea gravel?
Both are naturally rounded water-smoothed stones. However, pea gravel consists of very small pebbles (about 1/4 to 1/2 inch in size), whereas river rock refers to larger stones (ranging from 1 inch up to 5+ inches in diameter).
How do you clean river rock in landscaping?
To clean river rocks, hose them down with a high-pressure spray nozzle to wash away dirt. You can also use a leaf blower on low power to clear away fallen leaves and organic debris before they decay into compost.