Landscape Rock Calculator
Landscape rock volume is length × width × depth — about 2 in over weed fabric, 3 in without — and weight is volume × roughly 1.25 tons per cubic yard. A 30 × 4 ft border bed at 2 in needs 0.74 yd³ (≈ 0.9 tons), or 0.78 yd³ with 5% waste. For wood mulch, use the Mulch Calculator.
How it's calculated: Tons = length × width × depth (in yd³) × ≈ 1.25 t/yd³ (one typical figure; actual rock varies).
Result appears here
Fill in the fields and press Calculate.
Formula, calculation, assumptions and sources
Volume = Length × Width × Depth
Weight = Volume × bulk density
Run the calculation to see each step with your own numbers.
A 30 ft × 4 ft border bed, 2 in of river rock, 5% waste.
Volume = 20 ft³ = 0.74 yd³ exact
Weight ≈ 0.74 × 1.25 ≈ 0.9 US tons
+5%: order 0.78 yd³
- Rectangular bed of uniform depth — for an irregular bed, break it into rectangles.
- Density varies a lot by rock type (light lava rock vs dense river cobble) — the weight uses one typical figure, so check your supplier's tons-per-yard for the exact rock.
- Weed fabric, edging and delivery are separate.
- Rock by the yard or by the ton?
- Bulk rock is usually priced per ton; bagged decorative rock is priced per bag (0.5 ft³ is common). The calculator gives both a volume and a weight so you can match your supplier.
- How deep should decorative rock be?
- About 2 inches over a weed barrier for a decorative cover, or 3 inches with no fabric so weeds can't push through. Deeper than that just wastes stone and is hard to walk on.
- How much landscape rock do I need?
- Multiply the bed's length × width × depth in feet and divide by 27 for cubic yards. A 30 × 4 ft bed at 2 in deep needs 0.74 yd³ — about 0.9 tons of river rock at 1.25 t/yd³.
- How many square feet does a ton of landscape rock cover?
- About 130 ft² at 2 in deep, assuming about 1.25 tons per cubic yard. At 3 in deep a ton covers roughly 86 ft². Lighter lava rock covers more; dense river cobble covers less.
Volume
Standard geometry: Volume = L × W × D. Unit conversions per NIST SP 811.
Bulk density
Decorative landscape rock ≈ 1.25–1.35 t/yd³ (≈1,500 kg/m³). Landscape-supply industry figures. Varies by rock type and size.
About the Landscape Rock Calculator
The Landscape Rock Calculator gives the volume and weight of decorative stone — river rock, lava rock, cobble or crushed granite — for a planting bed or ground-cover area. Density varies a lot between light lava rock and dense river cobble; the weight uses one typical figure (≈ 1,500 kg/m³), so treat it as an estimate and confirm with your supplier. Weed fabric, edging and delivery are separate.
What you enter
- Length
- Width
- Depth — 2 in for a decorative cover over fabric; 3 in if there's no weed barrier.
- Waste allowance — Default 5%. Adjust to your own allowance — the exact figure is always shown too.
What you get back
- Volume — shown as the exact figure and, separately, a recommended figure with your waste allowance added.
- Weight — Suppliers usually sell by weight. Weight uses one typical density for decorative rock (≈ 1,500 kg/m³) — lava rock is lighter and river cobble heavier, so confirm with your supplier.
The formula, a worked example, the assumptions behind it and the sources are shown in full below the calculator.
Related calculators
- Mulch Calculator — Mulch in cubic yards and cubic feet for a bed of a given area and depth.
- Gravel Calculator — Gravel by volume and by delivered weight for driveways, paths and fill.
- Crushed Stone Calculator — Crushed stone by volume and weight. Shares the density question with the Gravel Calculator.
Related articles
- Gravel Sizes Explained: Which Size Do You Need? — Gravel comes in a range of standard sizes, each suited to a different job — drainage stone, base material, and decorative surface stone all differ.
Part of the Landscaping & Driveway calculators.