The formula
Cubic feet = length (ft) × width (ft) × depth (in) ÷ 12. Cubic yards = cubic feet ÷ 27. For a circle, area = π × (diameter ÷ 2)². We add a waste allowance (default 10%) before converting.
Weight assumptions
| Material | Typical tons per cubic yard used | Range |
|---|---|---|
| Gravel | 1.4 | 1.3–1.5 |
| Mulch | 0.3 | 0.2–0.4 |
| Topsoil | 1.1 | 0.9–1.25 |
| Sand | 1.35 | 1.25–1.5 |
Density varies with type, grading and moisture. These are typical working figures, not guarantees. Two landscape suppliers publish about 400 to 800 lb per cubic yard for mulch, 1,800 to 2,500 lb for topsoil, 2,500 to 3,000 lb for sand and 2,600 to 3,000 lb for gravel; the Washington State DOT design manual gives 1.40 to 1.55 tons per loose cubic yard for gravel; an Ohio State extension article gives about 100 lb per cubic foot for sand and nearly one ton per cubic yard for topsoil. Our mulch figure is toward the middle of the suppliers' range and is the least certain.
Depths and bag sizes
Project depths come from extension services and the Interlocking Concrete Pavement Institute. Bags are 2 cubic feet for mulch, 0.75 for topsoil, and 0.5 for sand and pea gravel, which are the sizes we could confirm on a national retailer's site; other sizes exist, and you can change the bag size in the calculator. Bulk is sold by the cubic yard, which is 27 cubic feet.
What we could not confirm
We found no official standard for the depth of a home sandbox, so the sandbox pages use 6 in as a minimum and say so. We could not confirm a national bulk-delivery minimum or fee, so we do not state one. Coverage rules of thumb vary: exact maths gives about 108 square feet per cubic yard at 3 in, while some sources round to 100.
Sources
- Washington State DOT Design Manual, Exhibit 620-1 (aggregate unit weights, loose and compacted, and a 10% stockpile-waste note)
- Ohio State Extension, Fairfield County Master Gardeners: Garden geometry
- Round Rock Landscape Supplies: bulk material delivery guide
- Harbor Soils: cubic yard calculator guide
- ICPI Tech Spec 10: base and bedding depths
- University of Maine Extension: stone path layers
- City of Elgin: shed gravel base guide
- University of Georgia: mulch depth and mulch volcanoes, Penn State Extension, Iowa State Extension
- Penn State Extension: lawn establishment, New Mexico State University
- Utah State Extension: raised bed gardening, University of Maryland Extension
- Mississippi State Extension: mulch quantities and bag sizes, Iowa State Extension: how much mulch
- Menards: bagged mulch, topsoil and sand sizes
Figures checked against these sources on 7 November 2026. Estimates only: always confirm quantities with your supplier.