Landscape Rock Calculator
Decorative rock by volume and weight for a landscaped bed.
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) — adjust it if your supplier gives you a figure.
- 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.
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, so adjust the figure if your supplier gives you one. 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 the material's bulk density (adjustable).
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 or bags 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.
Part of the Landscaping & Driveway calculators.