Work out how much decorative rock or stone you need for a bed, border or path. Choose the type, enter your area and depth, and get tons, cubic yards and bags.
Extra to cover gaps and cost
Weights are typical for dry, loose material. Your supplier's figure may differ slightly.
Why the type of rock matters so much
Two beds the same size can need very different tonnage. Lava rock is full of air pockets and weighs less than half as much as most stone, so a ton of it goes more than twice as far. That’s why the calculator asks for the type before it gives you tons.
| Rock or stone | Weight per cubic yard | 1 ton covers at 2 in | 1 ton covers at 3 in | 0.5 cu ft bags per ton |
|---|---|---|---|---|
| Lava rock | about 0.60 tons | 270 sq ft | 180 sq ft | about 90 |
| River rock | about 1.35 tons | 120 sq ft | 80 sq ft | about 40 |
| Mexican beach pebbles | about 1.35 tons | 120 sq ft | 80 sq ft | about 40 |
| Marble chips | about 1.40 tons | 116 sq ft | 77 sq ft | about 39 |
| Crushed granite | about 1.40 tons | 116 sq ft | 77 sq ft | about 39 |
Coverage figures have no extra added for gaps.
Worked example
A 10 ft × 10 ft bed, 3 inches deep:
- 10 × 10 × 3 ÷ 12 = 25 cubic feet, or 0.93 cubic yards
- With 5 percent extra: 0.97 cubic yards
- In lava rock: 0.97 × 0.60 = about 0.58 tons
- In river rock: 0.97 × 1.35 = about 1.31 tons
Same bed, same depth, but more than twice the weight in river rock.
Choosing a decorative rock
- Lava rock: red or black, light and easy to spread. It holds heat, so it suits dry gardens and fire pit surrounds. Its rough edges are hard on bare feet.
- River rock: smooth and rounded in mixed natural colors. See the river rock calculator for depths by rock size.
- Mexican beach pebbles: very smooth, dark grey to black stones. They look striking in small areas and are usually sold in bags or by the pallet.
- Marble chips: bright white. Marble can slowly make soil more alkaline, so keep it away from acid-loving plants such as azaleas and blueberries.
- Crushed granite: angular pieces that lock together a little, making a firmer surface for paths.
Rock, stone or gravel?
Suppliers use these words loosely, and there’s no strict rule. This calculator is for loose rock spread as a ground cover, worked out by area and depth. Walls built from stone or block need a different calculation based on block size and wall height.
Frequently asked questions
How much does a ton of landscape rock cover?
For most stone, about 80 square feet at 3 inches deep or 120 square feet at 2 inches. Lava rock covers far more: about 180 square feet at 3 inches.
How many bags of rock are in a ton?
About 40 bags of 0.5 cubic feet for river rock or beach pebbles, and about 90 bags for lava rock, because it’s much lighter.
How deep should decorative rock be?
About 2 to 3 inches for small rock. Larger rock needs a deeper layer, roughly as deep as the rocks are big, so the ground doesn’t show through.
Is landscape rock better than mulch?
Rock lasts for years and won’t blow away, but it doesn’t improve the soil and it gets hot in full sun. Mulch breaks down and needs topping up, but it feeds the soil and keeps roots cool.
Do I need landscape fabric under rock?
It’s recommended. Fabric slows weeds and stops the rock sinking into the soil.
Results are estimates for planning. Weights are typical for dry, loose material. See How We Calculate for the formulas and values we use.