River Rock Calculator
Estimate river rock in tons and cubic yards for landscaping, ground cover, and drainage features.
Your River Rock Estimate
- Enter area — length and width of the space to cover.
- Set depth — 2–3" for ground cover, 4–6" for creek beds and drainage.
- Adjust density — 130 lb/ft³ is average. Larger stones leave more air gaps and weigh less per ft³.
- Add waste — 10% standard. River rock doesn't compact much — less waste than gravel.
- Plan for delivery — river rock is heavy. Confirm the truck can access your site.
Planning a River Rock Project
River rock is naturally rounded stone tumbled smooth by water, ranging from 1 inch to 6+ inches in diameter. Its organic look makes it ideal for dry creek beds, water features, border accents, and ground cover around plantings. Unlike mulch, river rock doesn't decompose, blow away, or need annual replacement.
The main cost consideration is that river rock is significantly more expensive per cubic yard than crushed gravel — typically $40 to $100+ per ton depending on size and color (compared to $20–$40 for basic gravel). But since it's a permanent installation, the long-term cost is competitive with materials that need regular replacement.
River Rock Sizes and Applications
River rock comes in graduated sizes. Choosing the right diameter matters for both appearance and function:
| Size | Diameter | Weight | Best For |
|---|---|---|---|
| Small | 1–2 in | ~130 lb/ft³ | Ground cover, between pavers, garden beds |
| Medium | 2–4 in | ~120 lb/ft³ | Dry creek beds, borders, water features |
| Large | 4–8 in | ~110 lb/ft³ | Accent boulders, erosion control, retaining edges |
| Cobble | 6–12 in | ~100 lb/ft³ | Decorative borders, stream channels, focal features |
Larger stones leave more air gaps between them, so they weigh less per cubic foot. This also means you may see landscape fabric through the gaps — plan depth accordingly.
Formulas
Volume-to-weight:
Cubic yards = Volume ÷ 27
Weight (tons) = Volume × Density ÷ 2,000
With waste = Results × (1 + Waste %)
Density decreases as rock size increases due to air gaps. Adjust density down for large cobble (100–110 lb/ft³).
Related Calculators
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Frequently Asked Questions
How deep should river rock be for ground cover?
2 to 3 inches for small river rock (1–2 inch diameter) over landscape fabric. For larger 3–4 inch stones, go 3 to 4 inches deep. The goal is full coverage with no fabric visible. Add 1 inch of depth for larger stone sizes to compensate for air gaps between rocks.
Should I put landscape fabric under river rock?
Yes, for decorative ground cover applications. Landscape fabric prevents weeds from growing up through the rock and slows the rock from sinking into the soil over time. Use a woven fabric (not plastic sheeting) that allows water to drain through. Pin the fabric with staples and overlap seams by 6 inches. Note that fabric eventually breaks down over 5–10 years and will need replacing.
How much river rock do I need for landscaping?
For ground cover, use 2–3 inches of river rock depth. One ton of river rock covers approximately 70–80 square feet at 2 inches deep. Use the calculator above for exact tonnage — enter your area dimensions and desired depth. River rock is typically sold by the ton for bulk orders, or by the bag for small projects.
What size river rock is best for landscaping?
Small river rock (¾–1 inch) works best for ground cover and walkways — it is easy to walk on and fills gaps well. Medium rock (1–3 inches) is popular for dry creek beds and accent areas. Large boulders (3+ inches) are used for borders and focal points. For drainage applications, larger rock allows better water flow.
Do I need landscape fabric under river rock?
For decorative ground cover and dry creek beds: yes, use a woven landscape fabric (3 oz or heavier). It separates rock from soil, slows weed infiltration, and significantly reduces how quickly rock sinks in over time. Avoid plastic sheeting — it blocks water and oxygen, kills soil biology, and creates runoff. For drainage applications (French drains, retaining wall backfill), skip the fabric and use clean angular stone without fines so water moves freely. Fabric will not stop all weeds forever, but it can make maintenance easier when paired with proper edging.