How to calculate topsoil
Multiply the area by the depth you want to fill, in the same unit, then convert to cubic yards (divide cubic feet by 27) or cubic meters.
Worked example: a 4 × 8 ft raised bed, 12 in deep
32 sq ft × 1 ft = 32 cubic feet, or 1.19 cubic yards. Add 10% for settling and you need about 1.3 cubic yards, or 47 bags of 0.75 cu ft.
How deep should topsoil be?
| Project | Depth |
|---|---|
| Top-dressing an existing lawn | ¼–½ in (0.5–1 cm) |
| New lawn from seed or sod | 4–6 in (10–15 cm) |
| Flower beds | 6–8 in (15–20 cm) |
| Vegetable beds and raised beds | 8–12 in (20–30 cm) or more |
Why add extra
Loose soil settles once it is watered and walked on, often by 10–20%. Fill raised beds slightly above the rim so they finish level after settling.
Topsoil by the ton
A cubic yard of dry, screened topsoil weighs roughly 1 to 1.3 tons; wet soil weighs more. Bagged soil is easy for small beds, but a single cubic yard is about 36 bags of 0.75 cu ft, so bulk delivery quickly becomes cheaper for lawns and large beds.
For raised vegetable beds, plain topsoil can compact. Many gardeners mix it with compost.