How the soil calculator works
Buying soil comes down to one question: how much volume do you need to fill? This tool answers it with the same arithmetic a landscaper uses. It multiplies the area you are filling by the depth of the layer, then reports the result in the units suppliers actually sell in — cubic feet, cubic yards, bags, and approximate weight.
The core formula is a volume calculation. Because depth is usually given in inches while length and width are in feet, the depth is converted to feet first (divide inches by 12):
Volume (ft³) = length (ft) × width (ft) × (depth in inches ÷ 12)
To convert cubic feet to cubic yards, divide by 27, because a cubic yard is a cube 3 feet on each side and 3 × 3 × 3 = 27. Bulk soil is priced per cubic yard, so this conversion tells you what to order from a landscape yard. To count bags instead, divide the total cubic feet by the size printed on the bag and round up.
Why depth matters more than you think
Volume scales directly with depth, so the depth choice usually drives the cost. Doubling the depth doubles the soil. Common depths: 2–3 inches of compost as a top dressing, 4–6 inches to establish a lawn or seed a bed, 8–12 inches for a raised bed where roots need room, and the full box height for a new raised bed on a hard surface.
Handy reference points
- 1 cubic yard = 27 cubic feet = about 0.7646 cubic meters (764.6 liters).
- 1 cubic yard covers about 108 ft² at 3 inches deep, 81 ft² at 4 inches, or 65 ft² at 5 inches.
- A 4 ft × 8 ft raised bed filled 10 inches deep needs about 26.7 ft³ ≈ 0.99 cubic yard of soil.
- Screened topsoil weighs roughly 2,000–2,700 lb per cubic yard; garden mixes and compost are lighter, and wet clay is heavier.
Buy a little extra
Freshly delivered soil settles and compacts after watering, and beds are rarely perfectly rectangular. Ordering about 5–10% more than the calculated volume avoids a second trip to the supplier for a small shortfall. This calculator reports the exact geometric volume; add your own margin on top.