Xeriscape Rock Coverage Calculator
Enter your bed’s length, width, and rock depth to find out how many tons of river rock, lava rock, or decomposed granite to order.
Measure straight across the widest point.
2-3 in of decorative rock is standard for xeriscape beds
Covers spillage and compaction. 5–10% is normal.
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Bags or bulk delivery?
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Coverage & weight
Material profile
Rock volume comes from the bed’s area, length times width, times the coverage depth, converted from cubic feet to cubic yards. That volume is multiplied by the chosen rock’s weight per cubic yard, adjusted for a waste allowance, to get the total tons to order.
Rock Size and Coverage by Type
Different rock sizes cover different amounts of ground per ton at the same depth. Use this as a general planning reference alongside the calculator above.
| Rock Size Class | Best Use | Approx. Coverage per Ton (2 in depth) |
|---|---|---|
| 3/8 to 3/4 in (pea gravel/small) | Pathways, mulched beds | ~100-120 sq ft |
| 1 to 3 in (river rock) | Ground cover, accent beds | ~90-110 sq ft |
| 3 to 5 in (cobble) | Dry creek beds, borders | ~60-80 sq ft |
| Decomposed granite (fines) | Compactable paths, beds | ~100-130 sq ft |
Decorative rock weight by type
| Type | Weight per yd³ | Best for | Drainage |
|---|---|---|---|
| River rock (1-3 in) | 2,600 lb | Most popular xeriscape ground cover | Excellent, no fines |
| Lava rock | 1,500 lb | Lightweight decorative cover, good drainage | Excellent, porous |
| Decomposed granite | 2,800 lb | Compactable pathways and beds | Poor once compacted (by design) |
Figures are for dry material. Wet or freshly delivered material can weigh noticeably more.
How to calculate decorative rock you need
- Measure the length and width of the bed you’re covering in rock.
- Set your coverage depth, typically 2 to 3 in for decorative ground cover.
- Add waste 5 to 10% to cover uneven ground and spillage during spreading.
- Convert the volume to tons using the rock’s weight per cubic yard, and round up for ordering.
Worked example
A 25 x 20 ft xeriscape bed with 3 in of river rock and 8% waste:
- Bed size25 x 20 ft
- Rock depth3 in
- Area500 sq ft
- Waste allowance8%
- Volume135.0 cu ft (5.0 cu yd)
- Weight6.5 tons
- Bagged alternative270 bags (50 lb each)
- Bulk delivered cost$637.50
Recommended depth by project
| Project | Recommended depth | Notes |
|---|---|---|
| Decorative ground cover bed | 2 to 3 in depth | Standard depth for river rock or lava rock over landscape fabric |
| Weed-suppression cover | 3 to 4 in depth | Deeper layer needed to fully block light and suppress weeds |
| Walking path or stepping area | 3 to 4 in depth | Use angular crushed stone rather than round rock for underfoot stability |
| Dry creek bed or drainage swale | 4 to 6 in depth | Mix larger cobble with base rock to resist erosion during heavy rain |
Bags or bulk delivery?
Small beds and borders are often cheaper and easier in bagged rock, since you can buy exactly what you need and carry it without renting or borrowing a truck. Once a bed gets into the multi-ton range, like the 6.5 ton example above, bulk delivery is almost always the better deal and saves a lot of trips.
- Under 1 ton, go baggedsmall accent beds, borders, or a single tree ring rarely need more than a pallet of 50 lb bags.
- Over 2 to 3 tons, order bulkbulk pricing per ton drops fast, and most yards deliver straight to the driveway or bed location.
- Ask about a delivery minimumsome suppliers charge a flat delivery fee below a minimum tonnage, which can make bagged cheaper even at 1 to 2 tons.
- Plan a dump spot with driveway accessbulk loads get dumped in one pile, so make sure there’s a clear spot for the truck to reach before delivery day.
Common mistakes
- Skipping landscape fabricrock without a fabric barrier lets weeds grow up through the gaps within a season or two, undoing the low-maintenance point of xeriscaping.
- Choosing rock color without checking heat gaindark rock like lava rock or black basalt absorbs and radiates more heat, which matters right next to a house foundation or patio in hot climates.
- Not edging the bedwithout a physical border, rock migrates into the lawn where it becomes a mower hazard, and mulch or soil migrates into the rock bed.
- Underestimating depth on sloped bedsrock settles and washes downhill on a slope faster than on flat ground, so sloped beds often need extra depth or a check dam.
What this calculator assumes
Adjust your result if your project differs from these.
- The bed is measured as a simple rectangle: length times width.
- Coverage depth is uniform across the entire bed.
- A single waste percentage covers spillage and uneven spreading loss.
- Landscape fabric, edging, and bed prep are not included in this material estimate.
- Material weight per cubic yard is based on the selected rock type’s typical dry weight.
Common questions
How deep should xeriscape rock be?
2 to 3 in is standard over landscape fabric for most decorative beds. Go deeper, 3 to 4 in, if you’re relying on the rock alone to block weeds.
What's the difference between river rock and lava rock?
River rock is denser and heavier per cubic yard with a smooth, rounded look. Lava rock is lighter, porous, and often used where weight or heat retention matters.
Do I need landscape fabric under the rock?
Yes, for weed suppression. Rock alone, even at a good depth, won’t stop weeds from working through the gaps over time.
Is decomposed granite good for xeriscaping?
Yes, especially for pathways since it compacts into a firm, walkable surface. It drains less freely than loose rock once compacted.
How much rock do I need for a small border bed?
Small beds, under a ton or so, are usually cheaper and easier to handle in bagged rock rather than ordering bulk delivery.
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Xeriscape Rock Coverage Calculator Estimate
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materialcalculate.com/tools/xeriscape-rock-coverage-calculator/
Project
| Shape | — |
| Dimensions | — |
| Depth | — |
| Area | — |
| Material | — |
| Waste allowance | — |
Volume & weight (incl. waste)
| Cubic yards | — |
| Cubic feet | — |
| Weight | — |
| Tons (rounded up) | — |
Shopping list
| Bulk order | — |
| Bagged alternative (0.5 cu ft) | — |
| Estimated cost | — |
Notes
Estimate generated by materialcalculate.com. Assumes uniform depth and standard dry material densities. Confirm quantities with your supplier before ordering.