How deep to go
| Use | Published figure | Source |
|---|---|---|
| Bed fill | the full height of the bed | – |
| One cubic yard of dirt at 6 in | covers 55 sq ft | homeguide.com |
A raised bed is a box, so the soil volume is length × width × height. HomeGuide notes that one cubic yard of dirt covers 55 sq ft at 6 inches deep. Soil settles after watering, so many gardeners top it up after the first few weeks.
Working it out
Cubic yards = area (sq ft) × depth (in) ÷ 12 ÷ 27. Tons = cubic yards × weight per cubic yard.
Example: 8 × 4 ft × 2 at 12 inches is 2.37 cubic yards of topsoil, about 2.56 tons at 1.08 tons per cubic yard.
Rochester Concrete Products' install guide adds 10% for compaction and uneven ground.
Common questions
How much gravel do I need for a raised bed soil?
Measure the area, choose a depth from the table above and enter both in the calculator. It gives cubic yards, tons and bags.
Should I order extra?
Rochester Concrete Products' install guide adds 10% for compaction and uneven ground. Loose stone also compacts, so a compacted layer needs more loose material than its finished depth suggests.
Related calculators
Sources
- https://homeguide.com/costs/fill-dirt-sand-topsoil-cost
- https://www.engineeringtoolbox.com/dirt-mud-densities-d_1727.html