Landscape Rock Calculator
Calculate the volume and weight of decorative stone, river rock, decomposed granite, and lava rock for landscaping and pathways.
Estimated Required
Base Estimate
With 10% Waste
How to Use This Calculator
Enter the length and width of the landscape bed in feet and the depth in inches. Select the rock type — different stones have very different densities, which affects the weight in tons. Add a waste factor for edge loss and irregular shapes.
Formula & Methodology
This calculator estimates decorative rock quantity by converting your project dimensions into cubic volume, then applying the selected material density and waste factor.
Volume (yd³) = (Length ft × Width ft × Depth in ÷ 12) ÷ 27
Weight (tons) = Volume × Material Density
With waste = Weight (tons) × (1 + Waste %)
Density values vary by rock type. See Sources & Assumptions below.
Sources & Assumptions
Formula: Standard volumetric calculation converted to cubic yards, multiplied by the selected material's bulk density.
Density values: Typical bulk density ranges published by landscape material suppliers. River Rock ≈ 1.35 t/yd³; Decomposed Granite ≈ 1.50 t/yd³; Lava Rock ≈ 0.65 t/yd³; Marble/Quartz Chips ≈ 1.40 t/yd³. Actual density varies by stone size, source, and mineral composition.
Lava rock note: Lava rock is a porous volcanic material — its low density (≈ 0.65 t/yd³) means the same cubic yard weighs significantly less than other materials. Confirm density with your supplier.
Waste recommendation: 10% for rectangular decorative beds; 15% for irregular shapes, slopes, or areas with many plant obstructions.
Confirmation: Larger stone sizes have more air voids and may cover less area than calculated. Always verify coverage rate with your landscape supplier.
Last reviewed: May 2026
Recommended Depths & Coverage
Use these common depth ranges for planning. Actual depth may vary based on base conditions, compaction, drainage, and supplier recommendations.
| Project Type | Recommended Depth | Approx. Coverage per 1 yd³ | Notes |
|---|---|---|---|
| Decorative landscape rock | 2 in | ~162 sq ft | Typical coverage for visual ground cover |
| Weed suppression | 3 in | ~108 sq ft | Better coverage over fabric |
| Drainage rock | 4–6 in | ~54–81 sq ft | Depends on drainage need |
| Large river rock area | 3–4 in | ~81–108 sq ft | Larger stones need more depth |
Coverage values assume 1 cubic yard of material before waste. Add the selected waste factor for ordering quantities.
Project Examples
Common landscape rock applications with estimated quantities. Tonnage varies significantly by rock type — lava rock is roughly half the weight of river rock per cubic yard.
| Project | Dimensions | Depth | Est. Quantity |
|---|---|---|---|
| Decorative rock bed | 10 × 15 ft | 2 in | ~0.9 yd³ / ~1.3 tons |
| Drainage strip | 20 × 4 ft | 4 in | ~1.0 yd³ |
| Landscape border path | 30 × 5 ft | 3 in | ~1.4 yd³ |
Common Ordering Mistakes
- !Ignoring density differences between rock types: Lava rock weighs ~0.65 t/yd³ while river rock weighs ~1.35 t/yd³. Using the wrong density means a significantly different number on the delivery ticket — and a different cost.
- !Skipping landscape fabric: Installing rock without weed barrier fabric is one of the most common landscaping regrets. Adding fabric after the rock is placed is a multi-hour job. Install it first, before any rock goes down.
- !Ordering the same quantity as organic mulch: Rock provides similar visual coverage at 2–3 inches depth but is 3–4× heavier per cubic yard than mulch. Delivery cost, vehicle weight limits, and installation effort are all higher.
- !Using decorative rock for drainage: Ornamental river rock and lava rock are not clean, washed drain rock. French drains and drainage trenches require specifically graded drain rock or clean pea gravel to allow water to move freely.
- !Not adjusting depth for large stones: Stones over 3 inches in diameter need a deeper placement depth to fully cover the liner and achieve the visual coverage shown in the supplier's display. A standard 2-inch depth may leave the fabric visible.
Frequently Asked Questions
Related Calculators & Guides
Using topsoil under your decorative rock? Try the Topsoil Calculator. Prefer mulch for your beds? Use the Mulch Calculator. Need a gravel driveway estimate? See the Gravel Calculator.
Coverage chart, depth guide, and bed examples: How Much Rock Do I Need for Landscaping?
Disclaimer
Results are estimates only. Actual density varies by stone size, source, and mineral composition. Larger stones have more air voids and may cover less than calculated.