River Rock Calculator
River Rock Calculator
This calculator helps you estimate river rock volume, weight, and coverage for landscaping beds, pathways, drainage, and decorative ground cover. It also includes an optional cost estimate in USD.
River Rock Calculator
Estimate volume, weight, coverage area, and optional cost (USD)
Note
Density and coverage vary
River rock density changes with moisture, gradation, and voids. For pricing and delivery, confirm the unit your supplier uses (yard vs ton) and your desired finished depth.
Results
Enter dimensions above to calculate
What are river rocks?
River rocks are rounded stones found in streambeds and natural water channels. Years of water movement smooth the edges and create a variety of colors and textures. They’re commonly used for decorative beds, drainage layers, erosion control, and as ground cover.
How much river rock do you need?
The amount depends on the area you want to cover and the depth you plan to install. Measure your area, pick a finished depth, and add a waste allowance for irregular subgrade and spillage.
Different types of river rocks
River rock and decorative gravel densities vary by rock type and gradation. Use the table below as a reference, then confirm with your supplier for best accuracy.
| Rock type | Density (kg/m³) |
|---|---|
| Standard river rock | 1,425 |
| Bank gravel | 1,483 |
| Cheshire pink gravel | 1,545 |
| Congo river rock | 1,314 |
| Cotswold buff | 1,670 |
| Cotswold gold gravel | 2,098 |
| Crushed asphalt | 721 |
| Crushed granite | 1,320 |
| Crushed stone | 1,602 |
| Crystal river rock | 1,522 |
| Dolomite gravel | 1,865 |
| Granite | 2,650 |
| Ivory Coast gravel | 1,506 |
| Pea gravel | 1,788 |
| Peace river rock | 1,490 |
| Quartzite | 2,700 |
| Regular gravel | 1,346 |
| Sunset gold gravel | 1,505 |
| White marble chips | 1,430 |
How to use our river rock calculator
- Select a rock type (or Custom) to set density.
- Choose “How much river rock do I need?” to estimate volume/weight from area and depth.
- Or choose “How much area can I cover?” to estimate coverage from a known volume or weight.
- Enter depth and waste allowance, then optionally add a unit price in USD for cost.
How do you calculate river rock volume and weight?
The core calculation is volume from area and depth, then weight from density.
1. Select a river rock type (density)
Different river rocks and gravels have different densities. The calculator uses density to convert volume to weight (and vice versa). If your supplier provides a density, select Custom and enter it.
2. Calculate volume needed
Multiply the area to cover (A) by the depth (d), then add a waste allowance (c) for spillage, uneven subgrade, and minor measurement errors.
3. Convert volume to weight
Multiply the required volume by the selected density to estimate the total weight. Many suppliers sell decorative rock by the ton/tonne.
4. Coverage calculator (optional)
If you already have a known volume or weight of river rock, the calculator can estimate how much area it will cover at your chosen depth (after waste).
5. Cost estimate (optional)
Enter a unit price (USD) per yard/metre or per ton/tonne to estimate total project cost. Pricing varies by region, size, color, and delivery fees.
Sample calculation of the amount of needed river rock
Example: A walkway 0.8 m wide and 10 m long, depth 7.5 cm, pea gravel density 1,788 kg/m³, and 5% waste.
V = (A × d) × (1 + c) = (8.0 × 0.075) × 1.05 = 0.63 m³
W = V × ρ = 0.63 × 1,788 = 1,126.44 kg
FAQs
- How much river rock do I need?
- Measure the area you want to cover, choose a depth, and multiply area × depth to get volume. Then add a waste allowance. Multiply volume by rock density to estimate weight.
- What depth should river rock be?
- For decorative beds, 5–10 cm (2–4 in) is common depending on rock size. For drainage layers or heavier use, deeper sections may be required. Match depth to rock diameter and intended use.
- Do I buy river rock by the yard or by the ton?
- Both are common. Some suppliers sell by cubic yard/metre, others by ton/tonne. Use density to convert between volume and weight, and confirm units with your supplier.
- How much does a yard of river rock cost?
- Costs vary by region and rock type, but a cubic yard of river rock is commonly priced in the low hundreds of USD. Delivery, color, and sizing can significantly change the price.