Rock Calculator

Landscape Rock Calculator

Calculate cubic yards, tons, and bag counts for river rock, lava rock, crushed granite, flagstone, marble chips, slate, and limestone. Eight rock types with accurate density data.

The Short Answer: One cubic yard of landscape rock covers about 108 sq ft at 3 inches deep. River rock weighs roughly 2,700 lb per cubic yard (1.35 tons). Lava rock is much lighter at about 1,500 lb per yard. Always order by the ton for bulk — it's how quarries and landscape suppliers price it.

Rock Calculator

Enter your area dimensions, depth, and rock type.

Cubic yards
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Cubic feet
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Tons
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Bags
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Coverage
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Add 10% for irregular shapes, slopes, and settling. Bulk delivery minimums typically start at 1–2 tons.

8 rock types
Accurate density data

How to Calculate Landscape Rock

Landscape rock is ordered by the ton from quarries and landscape supply yards, but you measure your project area in square feet and depth in inches. Converting between area, volume, and weight requires knowing the density of the specific rock type — and landscape rocks vary widely. Lava rock at 55 lb per cubic foot is nearly half the weight of river rock at 100 lb per cubic foot.

Rock Type Comparison

Recommended Depths

Decorative rock beds and borders: 2–3 inches. Pathways and high-traffic areas: 3–4 inches. Drainage and erosion control: 4–6 inches. The bigger the rock, the deeper you need to go — 1-inch pea gravel works at 2 inches, but 3-inch river rock needs at least 3–4 inches to avoid bare spots.

Frequently Asked Questions

Enter your area dimensions and depth into the calculator above — it converts to tons automatically based on rock type. As a rough guide: one ton of average landscape rock covers about 80 square feet at 3 inches deep. But this varies significantly by rock type — a ton of lava rock covers nearly twice the area of a ton of river rock because it's so much lighter.

It depends on the rock type. River rock and crushed granite weigh about 2,700 lb (1.35 tons) per cubic yard. Marble chips are around 2,565 lb. Lava rock is the lightest at approximately 1,485 lb (0.75 tons) per cubic yard. Always confirm with your supplier — moisture content and rock size affect actual weight.

Gravel is typically crushed stone with angular edges — it compacts well and is used for structural base layers, driveways, and drainage. Landscape rock includes a broader range: river rock (smooth, rounded), lava rock (porous, volcanic), marble chips (decorative), and flagstone (flat). The distinction matters because gravel compacts and locks together, while decorative rock stays loose. Our Gravel Calculator handles crushed stone for base and drainage applications.

For decorative rock beds, yes — landscape fabric keeps rock from sinking into the soil and reduces weed growth. For drainage applications, use a permeable fabric that allows water through. For pathways with crushed granite, fabric prevents the DG from mixing into the subsoil. The one exception: don't use fabric under rock in planting beds where you want plants to root into the ground below.

The Bottom Line

Landscape rock is heavy and expensive to deliver, which makes accurate estimation critical. Overordering a ton of river rock means paying $50–$75 to move material you don't need. Underordering means a second delivery charge. Measure your area, choose your rock type, set the depth, and let this calculator convert to tons — the unit your supplier will quote. Add 10% for irregular edges and settling, and you'll order right the first time.

Gravel Calculator

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