How soil volume is calculated
Soil volume in cubic feet is length × width × (depth in inches ÷ 12), because depth is usually measured in inches while length and width are in feet. A 10 × 4 ft bed at 6 inches deep needs 10 × 4 × 0.5 = 20 cubic feet. Divide by 27 to get cubic yards (about 0.74).
More examples: an 8 × 4 ft bed at 12 inches deep needs 32 cubic feet, or 1.19 cubic yards, and a 4 × 4 ft bed at 8 inches deep needs about 10.7 cubic feet. For a round planter use π × radius² × depth in feet.
The compost calculator answers the question that usually follows this one.
Buying in bags vs bulk
Bagged soil is sold in cubic feet (often 1.5 cu ft per bag), while bulk delivery is priced per cubic yard. Knowing both numbers helps you compare cost. For a raised bed you can space plants with the plant spacing calculator.
At 1.5 cu ft per bag, that 20 cu ft bed takes 14 bags — enough that bulk delivery is often cheaper, though most suppliers set a minimum order. A cubic yard of topsoil weighs roughly 2,000–2,700 lb depending on moisture, which matters both for delivery access and for how much weight a raised bed frame has to hold.
How to use this calculator
Enter the bed length and width in feet and the fill depth in inches. The result shows cubic feet with cubic yards in the badge. Building a pond instead? See the pond volume calculator.
Most raised beds use a mix rather than pure topsoil; a common recipe is 60% topsoil, 30% compost and 10% perlite by volume.
Frequently asked questions
- How much soil for a 10x4 bed at 6 inches?
- About 20 cubic feet, or roughly 0.74 cubic yards.
- How do I convert cubic feet to cubic yards?
- Divide cubic feet by 27, since one cubic yard equals 27 cubic feet.
- Should I add extra for settling?
- Yes. Add about 5–10% because loose soil compacts after watering and over time.
- Does this work for compost or mulch?
- Yes — the volume math is the same for any loose material measured by length, width and depth.
- How many bags of soil is that?
- Divide the cubic feet by the bag size — 20 cubic feet is 14 bags at 1.5 cu ft each, or 10 bags at 2 cu ft. Buy one extra bag to cover settling after the first watering.