How Much Rock Do I Need for Landscaping?
River rock, decomposed granite, lava rock, and decorative stone are popular ground covers for landscape beds, paths, and drainage areas. This guide shows you how to estimate how many cubic yards and tons you need, with a coverage chart for common rock types and a worked example for a 10×15 ft bed.
The Formula
Volume (cu ft) = Length (ft) × Width (ft) × Depth (ft)
Depth (ft) = Depth (inches) ÷ 12
Volume (cu yd) = Volume (cu ft) ÷ 27
Weight (tons) = Volume (cu yd) × Density (t/yd³)
Worked Example: 10×15 ft Bed at 3 Inches
Bed size: 10 ft × 15 ft = 150 sq ft
Depth: 3 inches = 0.25 ft
Volume: 150 × 0.25 = 37.5 cu ft ÷ 27 = 1.39 cubic yards
River rock weight: 1.39 × 1.35 ≈ 1.87 tons
With 10% waste: 1.53 cubic yards / 2.06 tons — order 2 tons or 1.6 yards.
Lava rock (same dimensions): 1.39 × 0.65 ≈ 0.90 tons — much lighter, same volume.
Coverage by Rock Type at 3-Inch Depth
| Rock Type | Density (t/yd³) | Sq ft per ton | Sq ft per yd³ |
|---|---|---|---|
| River Rock | 1.35 | 109 | 108 |
| Decomposed Granite | 1.50 | 97 | 108 |
| Marble / Quartz Chips | 1.40 | 104 | 108 |
| Lava Rock | 0.65 | 236 | 108 |
At 3-inch depth. Volume per yard covers the same sq ft regardless of density — density only affects weight (and therefore cost-by-ton).
Recommended Depth by Application
Decorative accent (borders, pots) — 1–2 inches
Minimal coverage — mainly visual. Does not suppress weeds effectively.
Standard landscape beds — 2–3 inches
Good coverage. Use with landscape fabric for weed control.
Weed suppression without fabric — 3–4 inches
Deeper layer inhibits most weed seeds without needing fabric underneath.
Drainage / dry creek bed — 4–6 inches
Use larger river rock (2–4 inch diameter). Focus on consistent coverage over the drainage channel.
Calculate Your Exact Rock Quantity
Enter your bed dimensions, depth, rock type, and waste factor for instant cubic yards and tons.
Open Rock Calculator →Frequently Asked Questions
How much rock do I need for a 10×15 ft landscape bed?
At 3 inches deep: (10 × 15 × 3/12) ÷ 27 ≈ 1.39 cubic yards. At a river rock density of 1.35 t/yd³, that's about 1.87 tons. Add 10% waste — order approximately 1.53 yards or just over 2 tons. Use the Rock Calculator above for any size or depth.
How deep should landscaping rock be?
2–3 inches is standard for decorative ground cover. 3–4 inches is recommended for weed suppression without landscape fabric. Depths over 4 inches add cost without additional benefit and can harm plant roots by trapping heat and limiting moisture.
How many cubic yards of rock are in a ton?
It depends on the rock type. River rock ≈ 0.74 yd³/ton (1.35 t/yd³). Decomposed granite ≈ 0.67 yd³/ton (1.50 t/yd³). Lava rock ≈ 1.54 yd³/ton (0.65 t/yd³ — very light). Always ask your supplier for the density of the specific product you're buying.
What type of landscaping rock covers the most area?
Lava rock covers the most area per ton because of its low density (≈ 0.65 t/yd³) — a ton of lava rock gives you about 1.54 cubic yards. Dense materials like decomposed granite cover less per ton. For coverage per dollar, compare cubic yards across rock types rather than tons.
Do I need landscape fabric under decorative rock?
Landscape fabric is optional but helps suppress weeds. Woven polypropylene fabric works better than plastic sheeting (it allows water through). Without fabric, use a 3–4 inch depth of rock. Note that landscape fabric degrades over 5–10 years and can be difficult to remove once rock is placed on top.
How much does a cubic yard of river rock weigh?
River rock typically weighs approximately 2,700 lbs (1.35 tons) per cubic yard in dry, loose bulk conditions. Wet river rock can weigh 10–15% more. Your supplier will quote either by the ton or cubic yard — ask which unit they use before ordering.
Sources & Assumptions
Density values: Representative bulk density ranges used 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.
Waste factor: 10% for rectangular beds; 15% recommended for irregular shapes, slopes, or beds with many plant obstacles.
Confirmation: Density varies by stone source, size, and moisture. Always confirm coverage rate and density with your landscape supplier before ordering.
Last reviewed: May 2026
Related Calculators & Guides
Ready to calculate your order? Open the Rock Calculator for cubic yards, tons, and bag count from your dimensions.
Prefer organic ground cover? Use the Mulch Calculator or check How Much Mulch Do I Need?
Not sure how deep mulch should go? Mulch Depth Guide
How This Estimate Was Prepared
All volume estimates on this page use standard area and volume formulas — length × width × depth, converted to cubic yards by dividing by 27. Density values reflect typical supplier bulk density ranges for loose, dry decorative stone; actual density varies by rock type, size, and moisture. A 10% waste factor is applied to account for irregular bed shapes and spreading loss. Always confirm coverage rate and density with your landscape supplier before ordering. Last reviewed: May 2026.