River Rock Calculator
Work out how much river rock you need for a decorative bed, dry creek, or border, in cubic yards, tons, or delivered cost, based on your dimensions and rock size.
Measure straight across the widest point.
Adjust depth below if needed.
Covers spillage and compaction. 5–10% is normal.
Everything is calculated in your browser. Nothing you type is sent anywhere or stored.
Bags or bulk delivery?
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Coverage & weight
Material profile
A 20×6 ft decorative bed filled 3 inches deep with 1–2″ river rock needs about 1.11 cubic yards (1.65 tons with a 10% waste allowance). Larger 4–8″ cobble needs extra depth — plan on at least 6 inches so the rocks sit level instead of perched on the fabric.
River rock needed for common project sizes
Tons vary by rock size below, matched to the density of the material typically used for each project.
| Project | Depth | Cubic yards | Tons |
|---|---|---|---|
| Border edging strip (30×1 ft) | 2 in | 0.19 yd³ | 0.25 tons |
| Decorative bed (20×6 ft) | 3 in | 1.11 yd³ | 1.50 tons |
| Large decorative bed (15×15 ft) | 3 in | 2.08 yd³ | 2.83 tons |
| Dry creek bed (40×3 ft) | 4 in | 1.48 yd³ | 2.01 tons |
| Long dry creek bed (60×4 ft) | 4 in | 2.96 yd³ | 4.03 tons |
| Cobble accent border (50×2 ft) | 6 in | 1.85 yd³ | 2.55 tons |
River rock sizes, density and typical use
| Type | Weight per yd³ | Best for | Drainage |
|---|---|---|---|
| 1–2″ river rock | 2,700 lb | Borders, ground cover | Good |
| 2–4″ river rock | 2,720 lb | Drainage beds, dry creeks | Excellent |
| 4–8″ river cobble | 2,750 lb | Accent borders, erosion control | Excellent |
Figures are for dry material. Wet or freshly delivered material can weigh noticeably more.
How to calculate river rock you need
- Measure the bed or bank. Get length and width in feet, or diameter for a round bed.
- Pick a rock size. 1–2″ for borders, 2–4″ for drainage beds and creeks, 4–8″ cobble for accents.
- Set your depth. 2″ for edging, 3″ for a decorative bed, 4″ for a dry creek — larger rock needs more depth to look full.
- Add waste. The calculator adds 10% by default since round river rock leaves more void space than crushed stone.
- Check the delivery minimum. Most yards charge a flat delivery fee regardless of load size, so compare it against bagged cost for small orders.
Worked example
The calculator’s default scenario is a 20×6 ft decorative bed, 3 inches deep, using 1–2″ river rock.
- Area20 ft × 6 ft = 120 sq ft
- Depth in feet3 ÷ 12 = 0.25 ft
- Volume120 × 0.25 = 30 cu ft
- Cubic yards30 ÷ 27 = 1.11 yd³
- Material1–2″ river rock at 2,700 lb/yd³
- Tons before waste1.11 × 2,700 ÷ 2,000 = 1.50 tons
- Order with 10% waste1.50 × 1.10 = 1.65 tons
Recommended depth by project
| Project | Recommended depth | Notes |
|---|---|---|
| Project type | Depth | Notes |
| Border / edging strip | 2 in | Thin layer just enough to define an edge along beds or walkways |
| Decorative ground cover bed | 3 in | Standard depth for 1–2″ rock over landscape fabric |
| Dry creek bed | 4 in | Deeper bed hides the fabric and gives a natural streambed look |
| Drainage swale or French drain cover | 4–6 in | Larger 2–4″ rock needs more depth to handle water flow |
| Cobble accent border (4–8″ rock) | 6–8 in | Big cobble needs extra depth so rocks sit level, not perched on top |
Bags or bulk delivery?
At $6 a bag (roughly 0.5 cu ft, ~50 lb each), bagged river rock costs about $240 per ton equivalent, versus roughly $58 per ton plus a $75 delivery fee in bulk. The crossover is around 0.41 tons (about 16 bags) — below that, bags are cheaper; above it, bulk wins.
- Small (under 0.5 tons)A short border strip — bags work fine, no delivery fee, and they’re easy to carry into tight side-yard access.
- Medium (0.5–3 tons)Most decorative beds and dry creeks — bulk usually wins past ~16 bags, but confirm delivery minimums, often 1–3 tons.
- Large (3+ tons)Long creek beds or big berms — bulk delivery only; ask about dump-and-spread versus wheelbarrow access for backyard jobs.
Common mistakes
- Using angular gravel instead of round river rock.It changes the whole look — river rock is tumbled and smooth, crushed stone is sharp-edged.
- Skipping landscape fabric.Rock sinks into soil and weeds grow through it within a season without a barrier underneath.
- Choosing rock too small for a creek bed.Under 2″ rock washes away in heavy rain; use 2–4″ minimum for drainage features.
- Not accounting for void space between round stones.Rounded rock still nests together loosely; add the 10% waste rather than ordering the bare minimum.
- Ordering by bag for a large bed.Bagged rock costs 3–5x more per ton than bulk once you’re past about half a ton.
- Ignoring the depth-to-size ratio.A 3″ deep bed filled with 4–8″ cobble leaves rocks sitting on top of exposed fabric instead of nestled in.
What this calculator assumes
Adjust your result if your project differs from these.
- Density is 2,700–2,750 lb per cubic yard depending on rock size.
- Depth is the finished, settled depth, not the loose-poured depth.
- Waste factor defaults to 10% to cover the extra void space between round stones.
- Bags are assumed to hold about 0.5 cu ft (~50 lb) each.
- The area entered is the rock coverage footprint only.
- The calculator assumes a flat, prepared sub-base; add extra for excavation or slope.
Common questions
What size river rock should I use for a dry creek bed?
2–4″ is the standard, mimicking real streambeds; mix in a few 4–8″ pieces as accents.
How deep should river rock be for landscaping?
3 inches is typical for a decorative bed, 2 inches for edging, and 4 inches for a creek bed.
Do I need landscape fabric under river rock?
Yes. It stops the rock from sinking into the soil and cuts down significantly on weed growth.
How much does a ton of river rock cover?
About 80 sq ft at a 3-inch depth using 1–2″ rock.
Is river rock good for drainage?
Larger 2–4″ rock and cobble drain excellently thanks to their void space; rock under 1″ drains less freely.
Can I put river rock over mulch?
It’s not recommended — mulch decomposes and mixes with the rock, making the bed hard to clean or rake.
How much heavier is river rock than crushed gravel?
Densities are similar (2,700–2,750 lb/yd³ vs. roughly 2,700 lb/yd³ for gravel); size and shape differ more than weight.
Should I buy river rock in bags or bulk?
Bulk is cheaper above about 0.4 tons (roughly 16 bags); bags are fine for touch-ups or tight-access spots.
Will river rock sink into the ground over time?
Yes, without a fabric barrier, especially on soft or wet soil — add a geotextile layer on soggy ground.
How much waste factor should I add for round river rock?
10% is standard; use 12–15% for large cobble beds with irregular curves or edges.
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River Rock Calculator Estimate
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Project
| Shape | — |
| Dimensions | — |
| Depth | — |
| Area | — |
| Material | — |
| Waste allowance | — |
Volume & weight (incl. waste)
| Cubic yards | — |
| Cubic feet | — |
| Weight | — |
| Tons (rounded up) | — |
Shopping list
| Bulk order | — |
| Bagged alternative (0.5 cu ft) | — |
| Estimated cost | — |
Notes
Estimate generated by materialcalculate.com. Assumes uniform depth and standard dry material densities. Confirm quantities with your supplier before ordering.