River Rock Calculator
Multiply the area (length x width) by the depth (converted to feet) to get cubic feet, divide by 27 for cubic yards, then multiply by the rock’s density (typically 1.2-1.5 tons per cubic yard) to get tons needed.
Quick Answer
Multiply the area (length x width) by the depth (converted to feet) to get cubic feet, divide by 27 for cubic yards, then multiply by the rock’s density (typically 1.2-1.5 tons per cubic yard) to get tons needed.
River Rock Calculator
Enter your bed dimensions and rock size below for an instant estimate, then see the formula, worked example, and common mistakes.
Enter your values and click calculate.
How to Use This Calculator
Measure length and width in feet; for irregular beds, break the space into rectangular sections and sum the areas.
2-3 inches is typical for decorative ground cover; 3-4 inches or more is common for drainage beds or areas with foot traffic.
Density realistically ranges from about 1.2 tons/cu yd for small washed rock to 1.5 tons/cu yd for large cobble — larger stone generally settles denser.
Suppliers often publish their own density figure for a specific product, which can differ from generic averages.
Formula
Cubic yards = (Length(ft) x Width(ft) x Depth(ft)) / 27, where Depth(ft) = Depth(in) / 12. Tons = Cubic yards x density (tons per cubic yard).
Reference Table: River Rock Size vs. Density
| Rock size | Approx. density | Typical use |
|---|---|---|
| 3/4 in (pea/small) | ~1.2 tons/yd3 | Walkways, small decorative beds |
| 1-3 in (medium) | ~1.3-1.4 tons/yd3 | General landscaping, drainage beds |
| 3-5 in+ (large/cobble) | ~1.4-1.5 tons/yd3 | Erosion control, accent borders |
Common Mistakes to Avoid
- Using a single “one size fits all” density figure — river rock density varies by roughly 1.2 to 1.5 tons per cubic yard depending on stone size and moisture, so always confirm with your supplier’s specific product.
- Forgetting to convert the depth measurement from inches to feet before multiplying with length and width in feet.
- Not adding extra for irregular bed shapes or depth variation across a sloped or uneven yard.
- Assuming bagged and bulk (by-the-yard) river rock have the same price per ton — bulk delivery is almost always cheaper per ton for larger projects.
When the Estimate May Be Wrong
Real river rock coverage depends on the specific stone size, moisture content, and how tightly it settles after placement — suppliers often list their own density figure for a given product, which can differ from generic averages. For large or critical drainage/erosion-control projects, confirm tonnage with your supplier’s product-specific weight chart before ordering.
FAQs
How many tons of river rock do I need per cubic yard?
It depends on stone size — roughly 1.2 tons per cubic yard for small (3/4 in) rock up to about 1.5 tons per cubic yard for large (3-5 in+) rock, with 1.3-1.4 tons/cu yd typical for common medium sizes.
How deep should a river rock landscaping bed be?
2-3 inches is typical for decorative ground cover; 3-4 inches or more is common for drainage beds or areas with foot traffic.
Is river rock sold by the ton or by the cubic yard?
Both — suppliers often quote by the ton for bulk delivery, but you can convert cubic yards to tons using the material’s density (tons per cubic yard) for that specific product.
Does river rock size affect how much I need?
Yes — larger rock has a different (often higher) density than smaller rock, and it also covers depth differently, so always match your calculator’s density setting to your chosen rock size.
Sources and Methodology
Density ranges (approximately 1.2 tons/cu yd for small/washed river rock up to 1.5 tons/cu yd for large cobble-sized river rock, with common medium sizes around 1.3-1.4 tons/cu yd) reflect published averages from multiple landscape-supply and aggregate-calculator references current as of 2026; always confirm the exact density with your specific supplier since it varies by stone type and moisture content.
