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Landscape Rock Calculator
Estimate how much decorative rock you need for garden beds, borders, paths and drainage areas. Pick the type of rock, enter the area and depth, and get tons, cubic yards and how far one ton goes.
Results are estimates. Soil, stone and mulch settle, weigh differently and vary by supplier. Confirm quantities and local requirements before ordering.
How to calculate it
Landscape rock is sold by the ton or the cubic yard. Multiply the length by the width in feet, then by the depth in feet (2 inches = 0.167 ft), and divide by 27 to get cubic yards. Multiply by the density to get tons.
Densities vary a lot: lava rock is light at around 0.7 tons per cubic yard, while river rock, decomposed granite and pea gravel are about 1.4. Ask your supplier for the exact figure for your product.
Worked example
A 20 ft × 5 ft bed of river rock 2 inches deep, with 10% extra:
| Area | 100 sq ft |
|---|---|
| Volume (no extra) | 0.62 cubic yards 16.7 cubic feet |
| Rock to order | 0.68 cubic yards includes 10% extra |
| Weight | 0.95 tons at 1.4 tons per cubic yard (river rock) |
| Coverage of one ton | 116 sq ft at 2 in deep |
| 0.5 cu ft bags | 37 bags |
| Cubic meters | 0.52 m³ |
How far does one ton of rock go at 2 inches deep?
| Rock | Tons per cubic yard | Coverage per ton |
|---|---|---|
| River rock | 1.4 | 116 sq ft |
| Decomposed granite | 1.4 | 116 sq ft |
| Pea gravel | 1.4 | 116 sq ft |
| White marble chips | 1.5 | 108 sq ft |
| Lava rock | 0.7 | 232 sq ft |
Tips
- Lay landscape fabric first to keep weeds down and stop the rock sinking into the soil.
- Use 2 to 3 inches for decorative beds. Thinner layers show the soil and fabric.
- Rock does not decompose like mulch, so you only buy it once, but it is hard to remove later.
- For flagstone and stepping stones, coverage depends on stone thickness, so ask the supplier for sq ft per ton.
Frequently asked questions
How much does a cubic yard of river rock weigh?
Roughly 1.4 tons (2,800 lb), though the exact weight depends on the stone size and moisture.
How many tons of rock do I need for 100 sq ft?
At 2 inches deep, 100 sq ft needs about 0.62 cubic yards, or roughly 0.86 tons of river rock before any extra.
How much does lava rock weigh?
Lava rock is light: about 0.7 tons (1,400 lb) per cubic yard, around half the weight of river rock.
How deep should decorative rock be?
2 to 3 inches for beds and borders. Decomposed granite paths are typically 2 to 4 inches, compacted.