Landscape rock calculator
A bed 20 ft long and 5 ft wide, 3 in deep, takes 0.93 cubic yards of rock. In river rock that is about 1.20 tons; in lava rock, about half the weight.
Same volume, different weight
Every rock covers the same area per cubic yard: 108 sq ft at 3 in deep. What changes is the weight, and so the tons you order and the trips in a pickup. Lava rock is full of air pockets and weighs about half as much as river rock.
| Rock | Lb per cu yd | Published range | Tons for 100 sq ft at 3 in | Sq ft per ton at 3 in |
|---|---|---|---|---|
| River rock | 2,600 | 2,570 to 2,700 | 1.20 | 83 |
| Pea gravel | 2,700 | 2,565 to 2,700 | 1.25 | 80 |
| Crushed stone (#57 and other clean stone) | 2,700 | 2,410 to 2,780 | 1.25 | 80 |
| Gravel (mixed sizes) | 2,700 | 2,565 to 2,700 | 1.25 | 80 |
| Lava rock | 1,350 | 1,030 to 1,730 | 0.63 | 160 |
River rock, gravel and crushed stone weights come from the EPA's conversion table and the Caltrans and MoDOT tables. Lava rock comes from bag labels: 0.5 cu ft bags weigh 19 to 32 lb depending on the brand and the size of the stones, so its range is wide; a supplier's figure for their rock is better. For decomposed granite, the decomposed granite calculator adds the extra it needs for compaction; for large stone on a bank or outfall, use the riprap calculator. For another rock, choose "Other" and enter its weight per cubic yard from your supplier.
Bags
| Item | Typical | Range | Stores | Per cubic yard |
|---|---|---|---|---|
| 0.5 cu ft bag of river rock | $6.49 | $4.99 to $6.99 | 6 | $350 |
| 0.5 cu ft bag of lava rock | $6.64 | $3.49 to $8.99 | 8 | $359 |
| 0.5 cu ft bag of pea gravel | $5.48 | $3.99 to $6.59 | 6 | $296 |
| 0.5 cu ft bag of gravel | $6.90 | $5.98 to $7.20 | 3 | $373 |
Landscape rock in bags is sold by volume, mostly 0.5 cu ft, so a cubic yard is 54 bags; the last column is that yard at the typical price. Compare it with your supplier's delivered price per yard before you buy bags for a large bed.
Sources
- Standard Volume-to-Weight Conversion Factors, U.S. Environmental Protection Agency, March 2016. Loose weights of gravel, rock, sand, sandy loam soil and shredded wood chips.
- Maintenance Manual Volume 1, Appendix: Useful Information, California Department of Transportation, July 2014. Loose weights of crushed gravel, limestone, granite, screenings, sand and soil; 111 lb of asphalt mix per square yard per inch; 2.0 tons per compacted cubic yard of base.
- Highway Maintenance Tables and Conversion Factors (Engineering Policy Guide appendix), Missouri Department of Transportation, current guide. Loose and compacted weights of crushed stone, sand, asphalt and concrete in pounds per cubic foot and per cubic yard.
- Online store listings for bagged concrete, mortar, grout, block, rebar, mesh, gravel, sand, soil, mulch and pavers, Google Shopping results (Home Depot, Lowe's, Menards, Ace Hardware, Walmart and others), November 2026. Single-item prices by store; the calculators use the median as the default and show the range.
- How Much Compost, Soil or Mulch Do I Need to Purchase?, Texas AgriLife Extension Service, Travis County, February 2010. Square feet times depth in inches, divided by 324, gives cubic yards.