How to calculate landscape stone
- Measure the bed or border in feet. For curving beds, lay a garden hose along the edge, then measure it as a few rectangles or a circle.
- Pick a depth that suits the stone size (see the table below). Bigger stones need a deeper layer to cover the fabric underneath.
- Choose the stone type. Volume converts to tons using that stone's weight; lava rock weighs about a third as much as river rock.
- Add about 10% to fill gaps and low spots.
Stone formula
Tons = Cubic yards × Tons per cubic yard
Worked example: a river rock border
A border 15 ft long and 6 ft wide at 3 in deep is 15 × 6 × 3 ÷ 324 = 0.83 cubic yards. With 10% extra that is 0.92 yards; at 1.35 tons per yard, order about 1.24 tons of river rock — or roughly 50 bags of 0.5 cu ft.
How deep should landscape stone be?
| Stone size | Examples | Recommended depth |
|---|---|---|
| Under ½ in | Pea gravel, decomposed granite, small chips | 2 in |
| ½–1 in | Crushed granite, marble chips, small river rock | 2–3 in |
| 1–2 in | River rock, beach pebbles, lava rock | 3 in |
| 2–4 in | Large river rock, cobbles | 4–5 in |
| 4–8 in | Cobblestone, small boulders for swales | 6 in or more |
A useful rule: the layer should be at least about twice the diameter of the stones so they overlap and hide the landscape fabric.
Stone types and weights
| Stone | Tons per cubic yard | Notes |
|---|---|---|
| River rock | ≈ 1.35 | Rounded and smooth; good for dry creek beds and drainage |
| Crushed granite or limestone | ≈ 1.4 | Angular; locks together for paths |
| Decomposed granite | ≈ 1.3 | Fine; compacts into a firm walking surface |
| Marble chips | ≈ 1.4 | Bright white; can raise soil pH near acid-loving plants |
| Beach pebbles | ≈ 1.4 | Smooth, flat; often sold by the bag |
| Lava rock | ≈ 0.5 | Very light and porous; a yard weighs about 1,000 lb |
Coverage per ton
At about 1.4 tons per cubic yard, one ton of stone covers roughly 116 sq ft at 2 in deep, 77 sq ft at 3 in and 58 sq ft at 4 in. Lava rock covers about three times as much area per ton because it is so light.
Installation tips
- Remove weeds and grass, then lay a woven landscape fabric to slow weeds and stop stone sinking into soil.
- Install a solid edging — steel, aluminum or stone — so rock doesn’t migrate into the lawn.
- Keep stone a few inches away from house siding; it can splash soil and hold heat against walls.
- For paths and driveways, use angular gravel or crushed stone instead of round rock, which rolls underfoot.
Frequently asked questions
How much landscape rock do I need?
Multiply length × width in feet by depth in inches and divide by 324 for cubic yards, then multiply by the stone’s weight per yard. A 15 × 6 ft bed at 3 in deep needs about 0.83 cubic yards, or about 1.1 tons of river rock before extra.
How many square feet does a ton of river rock cover?
About 80 sq ft at 3 in deep, or 120 sq ft at 2 in deep, depending on stone size.
How many bags of rock make a yard?
A cubic yard is 27 cu ft, so it takes 54 bags of 0.5 cu ft or 27 bags of 1 cu ft.
How deep should river rock be?
Generally 2–3 in for small river rock and 3–5 in for 2–4 in stones, so the stones fully cover the fabric underneath.
Is landscape rock sold by the ton or the yard?
Both. Quarries and landscape yards usually sell by the ton; some sell by the cubic yard, and garden centers sell bags. The calculator gives all three.
Sources & standards
This calculator's formulas and default values are based on the following codes, standards and published data. Codes are adopted and amended locally, so check with your building department for permitted work. See how we build and check our calculators.
- Aggregate and landscape suppliers’ published bulk weights for river rock, crushed stone, decomposed granite, marble chips and lava rock (typical values).
- University cooperative extension guidance on inorganic mulches and landscape fabric (for example, extension horticulture fact sheets on rock mulch).
- Unit conversion: cubic yards = sq ft × depth (in) ÷ 324; 1 yd³ = 27 ft³.