River Rock Calculator
Calculate volume, weight, and cost of river rock for your landscaping and drainage projects
Calculating the right amount of river rock is essential for landscaping projects and budget planning. Our river rock calculator helps you:
- Determine the volume of river rock needed based on area dimensions and depth
- Calculate the weight for transportation planning
- Estimate the number of bags required if purchasing bagged material
- Calculate the total cost based on current material prices
- Plan for different area shapes (rectangular or circular)
To use the calculator, select the river rock size, measurement unit, and area shape. Then enter the dimensions and depth. The calculator will instantly provide the area, volume, weight, number of bags, and estimated cost.
The basic formula for calculating river rock volume is:
Volume = Area × Depth
Where the area calculation depends on the shape:
- For rectangular areas: Area = Length × Width
- For circular areas: Area = π × (Diameter/2)²
The weight is then calculated by multiplying the volume by the density of the river rock:
Weight = Volume × Density
For bagged material, the number of bags is calculated by:
Number of Bags = Total Weight ÷ Weight per Bag
River rock comes in various sizes and types, each suited for different applications:
By Size
| Size Category | Dimensions | Best Uses |
|---|---|---|
| Pea Gravel | 1/8" - 3/8" (3-10 mm) | Pathways, playgrounds, between pavers, small water features |
| Small | 3/8" - 5/8" (10-16 mm) | Garden beds, walkways, small drainage areas |
| Medium | 3/4" - 1-1/2" (19-38 mm) | Landscaping, drainage, water features, ground cover |
| Large | 1-1/2" - 3" (38-76 mm) | Dry creek beds, drainage ditches, erosion control |
| Extra Large | 3" - 5" (76-127 mm) | Erosion control, large water features, decorative accents |
By Type
| Type | Characteristics | Typical Cost |
|---|---|---|
| Standard River Rock | Naturally tumbled, mixed earth tones | $40-75 per ton |
| Polished River Rock | Machine polished, enhanced colors | $100-200 per ton |
| Mexican Beach Pebbles | Dark, smooth, uniform appearance | $150-300 per ton |
| Decorative Colored Rock | Dyed in various colors | $80-150 per ton |
When selecting river rock, consider the visual appeal, functionality, and budget for your specific project. Smaller stones are generally less expensive and easier to work with, while larger stones provide better drainage and more dramatic visual impact.
The depth of river rock depends on its intended use:
Recommended Depths
| Application | Recommended Depth | Notes |
|---|---|---|
| Decorative Landscaping | 2-3 inches (5-7.5 cm) | Sufficient for visual appeal and weed suppression |
| Pathways | 2-4 inches (5-10 cm) | Deeper for high-traffic areas |
| Drainage Areas | 4-6 inches (10-15 cm) | Deeper for better water flow |
| Dry Creek Beds | 4-8 inches (10-20 cm) | Layer larger rocks on bottom, smaller on top |
| Around Plants | 2-3 inches (5-7.5 cm) | Keep away from plant stems/trunks |
Coverage Estimates
For quick reference, here's how much area a ton of river rock will cover at different depths:
| Depth | Coverage per Ton | Coverage per 50 lb Bag |
|---|---|---|
| 1 inch (2.5 cm) | 240 sq ft (22 m²) | 6 sq ft (0.56 m²) |
| 2 inches (5 cm) | 120 sq ft (11 m²) | 3 sq ft (0.28 m²) |
| 3 inches (7.5 cm) | 80 sq ft (7.4 m²) | 2 sq ft (0.19 m²) |
| 4 inches (10 cm) | 60 sq ft (5.6 m²) | 1.5 sq ft (0.14 m²) |
| 6 inches (15 cm) | 40 sq ft (3.7 m²) | 1 sq ft (0.09 m²) |
Note: These are approximate values based on average river rock density. Actual coverage may vary depending on the specific type and size of river rock.
River rock is versatile and used in various landscaping and construction applications:
Landscaping
- Ground cover for garden beds and borders
- Decorative mulch alternative around trees and shrubs
- Accent features in xeriscaping and low-maintenance landscapes
- Pathways and walkways
- Rock gardens and alpine gardens
Drainage Solutions
- Dry creek beds and drainage swales
- French drains and drainage ditches
- Rain garden components
- Erosion control on slopes and hillsides
- Foundation perimeter drainage
Water Features
- Pond and water garden edges
- Stream bed linings
- Waterfall construction
- Fountain bases and surrounds
- Aquarium and terrarium substrates
Functional Uses
- Weed suppression in garden beds
- Heat retention in garden beds
- Soil erosion prevention
- Decorative ground cover for areas where plants won't grow
- Pet-friendly yard covering (safer than mulch)
Decorative Applications
- Potted plant top dressing
- Terrarium and fairy garden elements
- Zen garden components
- Decorative vase fillers
- Mosaic and craft projects
- Prepare the area: Remove existing vegetation, rocks, and debris from the installation area
- Define borders: Install edging to contain the river rock and create clean boundaries
- Level the ground: Grade the area to ensure proper drainage away from structures
- Install weed barrier: Lay landscape fabric to prevent weed growth and soil mixing with the rocks
- Overlap fabric: Overlap seams by 6-12 inches and secure with landscape pins
- Consider drainage: For areas with water flow, create a slight slope or drainage channel
- Pour and spread: Add river rock in layers, starting with larger stones if using multiple sizes
- Maintain depth: Ensure consistent depth across the installation area
- Rinse if needed: Hose down the rocks to remove dust and enhance colors
- Maintenance: Periodically check for displaced rocks and add more as needed
Pro tip: For easier installation of bulk river rock, have it delivered as close as possible to the installation area. Use a wheelbarrow to transport the rock and a landscape rake to spread it evenly.
Several factors influence the cost of river rock for your project:
- Size and type: Larger sizes and specialty types (like Mexican Beach Pebbles) cost more
- Quantity: Bulk purchases generally cost less per unit than bagged material
- Quality: Cleaner, more uniform stones command higher prices
- Color: Dyed or specially selected colors cost more than natural mixed colors
- Transportation: Delivery distance significantly impacts the final cost
- Accessibility: Difficult access may require special equipment and increase costs
- Seasonality: Prices may fluctuate based on demand and availability
- Regional variations: Local availability and market conditions cause price differences
Typical cost ranges:
- Bulk river rock: $40-100 per ton for standard types
- Premium river rock: $100-300 per ton for specialty types
- Bagged river rock (50 lb): $4-8 per bag for standard types
- Premium bagged river rock: $8-20 per bag for specialty types
Cost comparison: Bagged river rock typically costs 2-3 times more per unit volume than bulk material. For projects requiring more than 1/2 ton (approximately 20 bags), bulk delivery is usually more economical despite delivery fees.
Additional costs: Don't forget to budget for landscape fabric ($0.10-0.30 per square foot), edging materials, and delivery fees ($50-150 depending on distance).
How much river rock do I need?
To calculate how much river rock you need, multiply the area to be covered (length × width for rectangular areas or π × radius² for circular areas) by the desired depth. For example, a 10 ft × 5 ft area with a 2-inch depth would require 10 × 5 × (2/12) = 8.33 cubic feet of river rock. For weight, multiply the volume by the density (typically 100-110 lbs per cubic foot). Add 5-10% extra for waste and settling.
How deep should river rock be?
The recommended depth for river rock depends on its purpose. For decorative landscaping, a 2-3 inch (5-7.5 cm) layer is typically sufficient. For drainage applications or walkways, 3-4 inches (7.5-10 cm) is better. For heavy drainage areas or dry creek beds, 4-6 inches (10-15 cm) or more may be necessary. Always install landscape fabric underneath to prevent weed growth and soil mixing with the stones.
How many bags of river rock do I need?
To determine how many bags of river rock you need, first calculate the volume in cubic feet (area × depth). Then divide by the volume per bag. A standard 0.5 cubic foot bag covers about 2 square feet at 3 inches deep. For a 50 lb bag, you'll get approximately 0.5 cubic feet of coverage. For example, if you need 10 cubic feet of river rock, you would need approximately 20 standard bags (10 ÷ 0.5 = 20).
What size river rock should I use?
The appropriate river rock size depends on your application: For pathways and high-traffic areas, 3/4" to 1-1/2" stones provide stable footing. For decorative beds, 1" to 3" rocks offer good coverage and visual appeal. For drainage areas and dry creek beds, 2" to 5" rocks allow proper water flow. For water features, 1" to 3" rocks work well for pond edges, while smaller 3/8" to 3/4" pebbles are better for stream beds. Smaller stones (pea gravel) are easier to walk on but may scatter more easily.
Is river rock better than mulch?
River rock and mulch each have advantages. River rock is more permanent, doesn't decompose, requires less maintenance, provides better drainage, and won't blow away in wind. However, mulch is less expensive initially, easier to install and remove, adds nutrients to soil as it decomposes, provides better weed suppression, and maintains more moderate soil temperatures. River rock is better for permanent landscaping features, drainage areas, and arid climates, while mulch is better for plant beds, areas where soil enrichment is desired, and budgets where frequent replacement is acceptable.