Landscape Rock Calculator
Work out the tons of decorative rock needed to cover your beds and borders.
What you'll need to order
- decorative landscape rock
- woven landscape fabric
- bed edging
Prices vary by region and haul distance. Get quotes from at least two local suppliers.
How this calculator works
tons = length × width × (depth ÷ 12) × 100 ÷ 2000
Most decorative rock averages 100 lb per cubic foot, about 2,700 lb per cubic yard. Lava rock is far lighter at roughly 50 lb per cubic foot — halve the result if that is what you are buying.
Worked example
With length 12 ft, width 8 ft, depth 3 in, this calculator returns 1.2 tons.
Landscape rock coverage by depth
Figures below assume length 10 ft × width 10 ft. Change any measurement in the calculator to get your own numbers.
| Depth | Rock needed (tons) | Volume (cu yd) |
|---|---|---|
| 1 in | 0.42 | 0.31 |
| 2 in | 0.83 | 0.62 |
| 3 in | 1.25 | 0.93 |
| 4 in | 1.67 | 1.23 |
| 6 in | 2.50 | 1.85 |
Per 100 square feet at 100 lb per cubic foot, a mid-range figure for decorative stone.
How much decorative rock for beds and borders?
| Job | Size | Rock needed | Material cost |
|---|---|---|---|
| Small accent bed | 10 ft × 4 ft × 3 in | 0.50 tons | $20 – $100 |
| Foundation border | 60 ft × 3 ft × 3 in | 2.25 tons | $90 – $450 |
| Front garden, no lawn | 30 ft × 20 ft × 3 in | 7.50 tons | $300 – $1,500 |
| Xeriscape conversion | 50 ft × 30 ft × 3 in | 18.75 tons | $750 – $3,750 |
| Slope erosion control | 40 ft × 12 ft × 4 in | 8.00 tons | $320 – $1,600 |
Three inches is the working minimum. Below that, fabric shows through and weeds find the gaps within a season.
Cost range uses $40–$200 per ton for material only.
What does landscape rock cost?
Material typically runs $40 to $200 per ton. Delivered, not spread. The range is wide because decorative stone is priced on appearance — colour consistency, not function.
What moves the price:
- Stone type: crushed granite and limestone at the bottom, imported marble chip and lava at the top
- Colour consistency and grading
- Haul distance, which dominates small orders
- Spreading labour, typically $40 to $80 per ton if you do not do it yourself
Prices are US averages and move with fuel, season and haul distance. Always get two local quotes before budgeting.
Decorative stone types and weights
| Type | Weight (lb per cu ft) | Notes |
|---|---|---|
| Crushed granite | 105.0 | Angular, stays put on slopes |
| River rock | 98.00 | Rounded, decorative, migrates |
| Limestone chip | 100.0 | Bright, raises soil pH over time |
| Marble chip | 105.0 | Premium white, stains over time |
| Lava rock | 50.00 | Half the weight for the same volume |
| Decomposed granite | 108.0 | Compacts to a firm path surface |
Weight matters when ordering by the ton. Lava rock covers roughly twice the area per ton of any other stone here — do not order it by weight without adjusting.
Frequently asked questions
How many tons of rock do I need per square foot?
About 0.025 tons per square foot at 3 inches deep, so 100 sq ft takes roughly 2.5 tons at 100 lb per cubic foot.
How long does landscape rock last?
Indefinitely, unlike mulch. What fails is the fabric underneath and the soil that blows in on top — most beds need cleaning or topping up every five to seven years, not replacing.
Can I put rock over existing mulch?
Not without removing it. Mulch keeps decomposing underneath, the level drops, and the rock sinks unevenly into what is left.
How much landscape rock do I need?
Multiply the bed area in square feet by the depth in feet, multiply by 100, then divide by 2,000 for tons. A 30 by 5 ft border at 3 inches deep needs a little under 2 tons.
How much does a ton of landscape rock cover?
At 2 inches deep, about 120 square feet. At 3 inches, roughly 80 square feet. At 4 inches, around 60 square feet. Lava rock covers roughly twice that area per ton because it weighs half as much.
How deep should decorative rock be?
Two inches for stone under an inch, three inches for larger stone. The rule of thumb is a depth of about one and a half times the stone diameter — enough to hide the fabric without wasting material.
Is rock or mulch better for landscape beds?
Rock lasts indefinitely and suits low-water planting, but it stores heat and adds nothing to the soil. Mulch feeds the soil as it breaks down but needs topping up yearly. Rock is the better choice around foundations and in arid climates.
How do I stop landscape rock sinking into the soil?
Lay woven landscape fabric first and edge the bed so the stone cannot migrate sideways. Without fabric, rock works into the soil within two or three seasons and you end up buying it twice.