Decorative rock and lava rock · depth, tons and prices
Landscape rock calculator
Enter length, width and depth to find how much landscape rock you need in cubic yards and US tons. The preset is 2,600 lb per yard for 3/4 inch decorative stone; lava rock weighs 36–60% as much, so switch the weight before you convert.
How much landscape rock you need
Enter your dimensions to see cubic yards, tons and bags
The short answer
How much landscape rock do I need?
Multiply length × width in feet by depth in inches, then divide by 324 for cubic yards. A 20 × 10 ft front yard bed at 2 in needs 33.33 ft³, or 1.23 cubic yards, which is about 1.6 US tons at the Granite Landscape Centers figure of 2,600 lb per cubic yard (1.3 tons per yard). The rock you choose changes the tonnage more than any rounding: the same bed in lava rock is 0.74 tons.
What extension services advise
How deep should landscape rock be?
2 to 3 inches for looks, 4 inches if it has to stop weeds. Three university extension services have published guidance on rock mulch, and they agree on less than you might expect: the depth differs by an inch or two, and they split on landscape fabric.
| Source | Depth | Landscape fabric | Heat and light |
|---|---|---|---|
| Colorado State University Extension | 4 in, for any mulch meant to suppress weeds | Not needed at the correct depth; woven fabrics “eventually become clogged” | Gravel passes more heat to the soil than wood chips, and to nearby buildings |
| Utah State University Extension | 2–3 in of inorganic mulch | Optional; choose fabric that lets air and water through, never plastic sheeting | Not addressed |
| University of California IPM | Not given | Recommended under rock, to stop stones sinking into the soil and soil rising into the rock | White rock reflects enough light to damage sensitive plants; dark rock holds heat |
Do you need landscape fabric under rock?
It depends which extension service you follow. Colorado State says rock at the correct depth needs no underlayment and that woven fabric clogs over time. UC IPM recommends fabric under rock because it stops stones sinking into the soil and soil working up between them. Utah State allows breathable fabric but rules out plastic sheeting. If you use fabric, the rock quantity does not change.
Colorado State also notes that stones larger than about half an inch do not work as mulch. For rounded rock and the depth suppliers plan for each stone size, see the river rock calculator; for a compacted path, the decomposed granite calculator.
The calculation
How to calculate landscape rock
- Measure the bed.Length × width in feet. Leave a few inches bare around the base of shrubs and trees; Utah State University Extension advises it to prevent root collar disease and rodent damage.
- Choose the depth.2 to 3 inches for decorative rock (Utah State), 4 inches where the rock has to hold back weeds (Colorado State). Rock larger than 2 inches goes about one stone deep.
- Convert to cubic yards.Length × width × depth in inches ÷ 324. A 20 × 10 ft bed at 2 inches is 1.23 yd³.
- Convert with the rock’s own weight.Crushed decorative stone here is 2,480–2,600 lb per yard; lava rock is 940–1,550 lb. Using a stone weight for lava roughly doubles the tonnage.
Rectangle · US measurements
Length × Width × Depth ÷ 324
Feet × feet × inches → cubic yards
Cubic yards × 2,600 ÷ 2,000
Cubic yards × lb/yd³ → US tons at the reference weight
Read the full calculation method ↗Worked examples
Landscape rock calculator examples
At 96.3 lb/ft³, before any allowance. Open one to load it into the calculator.
| Project | Volume | Weight |
|---|---|---|
| 20 × 10 ft front yard bed at 2 in | 33.33 ft³ · 1.23 yd³ | 1.6 US tons |
| 40 × 5 ft side yard at 3 in | 50 ft³ · 1.85 yd³ | 2.41 US tons |
| 12 × 12 ft area at 3 in | 36 ft³ · 1.33 yd³ | 1.73 US tons |
Bulk quantities
How much does a ton or a cubic yard of landscape rock cover?
One US ton at 2,600 lb per cubic yard is 0.77 cubic yards (20.77 ft³).
| Depth | One US ton covers | Tons for 100 ft² |
|---|---|---|
| 2 in | 124.62 ft² | 0.8 tons |
| 3 in | 83.08 ft² | 1.2 tons |
| 4 in | 62.31 ft² | 1.6 tons |
Why the density matters
How much does a yard of landscape rock weigh?
One cubic yard of landscape rock weighs 2,480 to 2,600 lb (1.24 to 1.3 US tons) across the published figures below, and 2,600 lb (1.3 US tons) at the calculator’s preset.
| Product | Publisher | lb per yd³ | Tons per yd³ |
|---|---|---|---|
| Desert Pearl 3/4 inch decorative rock | Granite Landscape Centers | 2,600 | 1.3 |
| Yuba Blue 3/4 inch decorative granite rock | Sutherland Landscape Supplies | 2,480 | 1.24 |
| Most landscape rock (general conversion) | Southwest Boulder & Stone | 2,500 | 1.25 |
Enter your supplier’s figure under Material & allowance. For gravel in general, see how much a yard of gravel weighs, which lists each supplier weight per yard in our ledger with its source and recorded date.
Published prices
How much does landscape rock cost?
Public price lists from 8 suppliers give a median of $75.00 per cubic yard ($56.00–$149.99, 7 prices from 4 lists) and a median of $73.98 per ton ($48.00–$185.00, 8 prices from 4 lists), before delivery. At this page’s reference weight of 2,600 lb per yard, the per-ton median works out to about $96.17 per cubic yard.
| Supplier | Product | Price |
|---|---|---|
| Harken's Landscape Supply East Windsor, CT | Marble Chips, approx. 3/4 inch | $80.00 per cubic yard Plus tax and delivery |
| Harken's Landscape Supply East Windsor, CT | CT Valley Blend, approx. 3/4 inch | $75.00 per cubic yard Plus tax and delivery |
| Down To Earth Materials Gray, TN | White Quartz 7/8 inch | $185.00 per ton Delivery $10 per mile |
| Texas Garden Materials Houston, TX | Rainbow Rock Gravel 3/8 - 1.5 inch | $149.99 per cubic yard Pickup; delivery at checkout |
| Bedrock Landscaping Materials Denver, CO | Black Granite 1.5 or 3/4 inch | $71.00 per ton Delivery extra (flat fee by distance) |
| Bedrock Landscaping Materials Denver, CO | Lyons Red 1.5 or 3/4 inch | $70.00 per ton Delivery extra (flat fee by distance) |
| Bedrock Landscaping Materials Denver, CO | Black Lava 1.5 inch | $185.00 per ton Delivery extra (flat fee by distance) |
| Ainsworth Rock Sales Denver, CO | Mountain Granite 3/4 or 1 1/2 inch | $76.95 per ton Delivery and tax not stated |
| Ainsworth Rock Sales Denver, CO | Colorado Rose 3/4 or 1 1/2 inch | $93.95 per ton Delivery and tax not stated |
| AZ Rock Express Apache Junction, AZ | Pink Coral 3/4 inch screened rock | $48.00 per ton Delivery by zone and tonnage |
| AZ Rock Express Apache Junction, AZ | Madison Gold 3/4 inch screened rock | $60.00 per ton Delivery by zone and tonnage |
| MRM Landscape Supply Ellensburg, WA | Red Rock (decorative) | $70.00 per cubic yard Pickup only; includes tax |
| MRM Landscape Supply Ellensburg, WA | Black Rock (decorative) | $80.00 per cubic yard Pickup only; includes tax |
| Sequoia Landscape Materials Santa Rosa, CA | Brown Lava 3/4 inch | $60.00 per cubic yard Delivery extra |
| Sequoia Landscape Materials Santa Rosa, CA | Brown Chip Rock 3/4 inch | $56.00 per cubic yard Delivery extra |
Per-ton and per-yard prices are not comparable until you convert with the product’s own weight per yard. Delivery fees, minimum orders and the other materials we track are on the gravel prices page.
Lava rock calculator
How much lava rock do I need?
The same cubic yards as any rock, but far fewer tons. Published lava rock weights from 6 suppliers run from 940 to 1,550 lb per cubic yard, against 2,480–2,600 lb for the crushed decorative stone above. At the middle figure of 1,200 lb, one ton covers about 270 ft² at 2 inches; a ton of the stone preset covers 125 ft². Load the 20 × 10 ft bed at 1,200 lb per yard.
| Product | Supplier | lb per yd³ | One ton covers at 2 in |
|---|---|---|---|
| Red Lava 1-3 inch | Main's Landscape Supply | 940 | 345 ft² |
| Red Lava Rock | Birch Tree Bark & Stone | 950 | 341 ft² |
| Black Lava 1-3 inch | Main's Landscape Supply | 1,200 | 270 ft² |
| Red Lava Rock | Suburban Landscape Supply | 1,200 | 270 ft² |
| Lava rock (red and black) | Landscape Centre | 1,250 | 259 ft² |
| Red Lava 3/8 or 3/4 inch | Sutherland Landscape Supplies | 1,420 | 228 ft² |
| Lava Rock, Red Hills | North Bay Materials | 1,550 | 209 ft² |
Why lava rock looks expensive per ton
Because a ton of it is a lot of rock. Main's Landscape Supply in Southfield, MI prints both a per-ton price and a weight per yard on each product page, so the per-yard price needs no outside assumption. Its red lava costs more per ton than its Canadian Marble 1–2 in and Rose Granite 1/2–1 in, yet it is the cheapest of them per cubic yard.
| Product | Per ton | lb per yd³ | Per cubic yard |
|---|---|---|---|
| Black Lava 1–3 in | $635.00 | 1,200 | $381.00 |
| Red Lava 1–3 in | $414.00 | 940 | $194.58 |
| Canadian Marble 1–2 in | $264.00 | 2,400 | $316.80 |
| Rose Granite 1/2–1 in | $239.00 | 2,400 | $286.80 |
The same applies to the price list below. Lava at $185.00 per ton (Bedrock Landscaping Materials) is $86.95–$143.38 per yard across the published lava weights; Sequoia Landscape Materials sells it at $60.00 per yard.
Before you order
Frequently asked questions about landscape rock
Is white rock bad for plants?
It can be. University of California IPM warns that white rock reflects enough light to damage sensitive plants and that dark rock holds heat. Colorado State University Extension adds that gravel passes more heat into the soil and onto nearby walls than wood chips do.
Is landscape rock cheaper by the ton or by the yard?
Neither unit is cheaper in itself; the rock’s weight decides. At Main's Landscape Supply, red lava 1–3 in costs $414.00 per ton against $264.00 for marble, but at the weights the same pages print it works out to $194.58 per yard against $316.80.
References
- Desert Pearl 3/4 inch decorative rock: 2,600 lb/yd³, Granite Landscape Centers. Recorded September 23, 2026
- Yuba Blue 3/4 inch decorative granite rock: 2,480 lb/yd³, Sutherland Landscape Supplies. Recorded September 23, 2026
- Most landscape rock (general conversion): 1.25 US tons/yd³, Southwest Boulder & Stone. Recorded September 23, 2026
- Mulching, GardenNotes (reviewed April 2023), Colorado State University Extension
- Water-Wise Landscaping: Mulch (2007), Utah State University Extension
- Pest Notes: Weed Management in Landscapes (Publication 7441), University of California IPM
- Red Lava 1-3 inch: 940 lb/yd³, Main's Landscape Supply. Recorded September 24, 2026
- Red Lava Rock: 950 lb/yd³, Birch Tree Bark & Stone. Recorded September 24, 2026
- Black Lava 1-3 inch: 1,200 lb/yd³, Main's Landscape Supply. Recorded September 24, 2026
- Red Lava Rock: 1,200 lb/yd³, Suburban Landscape Supply. Recorded September 24, 2026
- Lava rock (red and black): 1,250 lb/yd³, Landscape Centre. Recorded September 24, 2026
- Red Lava 3/8 or 3/4 inch: 1,420 lb/yd³, Sutherland Landscape Supplies. Recorded September 24, 2026
- Lava Rock, Red Hills: 1,550 lb/yd³, North Bay Materials. Recorded September 24, 2026
- Canadian Marble 1–2 in: $264.00 per ton, 2,400 lb per yard, Main's Landscape Supply. Recorded September 24, 2026
- Rose Granite 1/2–1 in: $239.00 per ton, 2,400 lb per yard, Main's Landscape Supply. Recorded September 24, 2026
About these calculations
Written with AI assistance from the sources listed on this page. Each figure links to its source; recorded dates are shown with the figures or in the gravel weight and price ledgers, and the arithmetic is covered by automated tests. The 2,600 lb per cubic yard preset is Granite Landscape Centers’ approximate published weight for its Desert Pearl 3/4 inch decorative rock. How this page was made · Report an error