Landscape Rock Calculator
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1.05 tons of River rock 3/4"–1 1/2", 0.78 yd³, 42 bags
Includes 5% extra. In-place volume without the extra: 0.74 yd³.
How much landscape rock do I need?
Tons = Volume (yd³) × Density (tons per yd³)
For example, a 20 × 4 ft border plus a round bed 8 ft across covers 130.3 ft². At 2 inches of 3/4"–1 1/2" river rock with 5% extra, that is 0.84 yd³, or about 1.14 tons.
Rock weight, depth and coverage
| Material | tons / yd³ | Typical depth | ft² per ton at that depth |
|---|---|---|---|
| River rock 3/4"–1 1/2" | 1.35 | 2 in | 120 |
| River rock 1"–3" | 1.35 | 3 in | 80 |
| Cobbles / beach pebbles 3"–5" | 1.35 | 5 in | 48 |
| Lava rock | 0.55 | 3 in | 196 |
| Decomposed granite (DG) | 1.35 | 3 in | 80 |
| Marble / quartz chips | 1.4 | 2 in | 116 |
Weights are typical loose, dry figures. Rock is a natural product, so weights vary between quarries; use your supplier's figure when you have one.
How deep should landscape rock be?
- Small river rock and pebbles (up to 1 1/2"): 2 to 3 inches, about twice the stone size, so no fabric shows through.
- Larger river rock (1"–3"): 3 to 4 inches.
- Cobbles and beach pebbles (3"–5"): usually one stone deep, so depth is about the stone size.
- Decomposed granite: 2 to 4 inches for paths, laid in layers that are wetted and compacted.
- Lava rock: 2 to 3 inches. It is light enough to be sold by volume, so compare prices per yard.
Fabric and edging
A woven landscape fabric under rock slows weeds and keeps stone from sinking into the soil. The calculator adds 10% to the bed area so sheets can overlap. Edging length is the perimeter of the beds you enter; for beds that meet a wall or path on one side, you will need less.
Frequently asked questions
How much river rock do I need?
Multiply the bed area by the depth to get the volume, then convert to tons using the rock's density (about 1.35 tons per cubic yard). A common rule is a depth of about twice the stone size, so 2 to 3 inches for 3/4 to 1 1/2 inch river rock.
How many square feet does a ton of river rock cover?
At about 1.35 tons per cubic yard, one ton of river rock covers roughly 120 sq ft at 2 inches deep and 80 sq ft at 3 inches deep.
Do I need landscape fabric under rock?
A woven landscape fabric under rock slows weeds and stops the stone sinking into the soil. Buy about 10% more than the bed area so the sheets can overlap. The calculator shows the fabric area and the edging length for the beds you enter.
How much does lava rock weigh compared with river rock?
Lava rock is porous and much lighter, roughly 0.5 to 0.6 tons per cubic yard versus about 1.35 for river rock. It is usually sold by volume, so check whether your supplier prices it per yard or per ton.
How deep should decomposed granite be?
Paths and patios typically use 2 to 4 inches of DG, laid in layers that are wetted and compacted. Because it compacts, the calculator adds 15% to the loose volume by default.