A raised bed soil volume chart is useful when you are comparing common bed sizes or deciding whether bags or bulk soil make more sense. The chart below uses inside dimensions and shows theoretical soil volume before any allowance for settling.
For final ordering, measure your own bed because wall thickness and actual inside dimensions can differ from the nominal size shown on a product label.
Calculate your exact raised-bed volume →
Raised bed soil volume chart
| Bed size | 6 in depth | 9 in depth | 12 in depth | 18 in depth |
|---|---|---|---|---|
| 2 × 4 ft | 4 cu ft | 6 cu ft | 8 cu ft | 12 cu ft |
| 2 × 8 ft | 8 cu ft | 12 cu ft | 16 cu ft | 24 cu ft |
| 3 × 6 ft | 9 cu ft | 13.5 cu ft | 18 cu ft | 27 cu ft |
| 4 × 4 ft | 8 cu ft | 12 cu ft | 16 cu ft | 24 cu ft |
| 4 × 8 ft | 16 cu ft | 24 cu ft | 32 cu ft | 48 cu ft |
| 4 × 12 ft | 24 cu ft | 36 cu ft | 48 cu ft | 72 cu ft |
How the raised bed soil volume chart is calculated
Multiply the inside length by the inside width to find square footage. Convert the chosen soil depth from inches to feet, then multiply area by depth.
A 4 × 8 bed has 32 square feet of area. At 12 inches, or 1 foot, the volume is 32 cubic feet. At 6 inches, or 0.5 feet, it is 16 cubic feet.
Convert cubic feet to cubic yards
One cubic yard equals 27 cubic feet, so divide the chart value by 27. A 3 × 6 bed at 18 inches contains 27 cubic feet, exactly one cubic yard. A 4 × 8 bed at 12 inches contains 32 cubic feet, or about 1.19 cubic yards.
| Cubic feet | Cubic yards |
|---|---|
| 9 | 0.33 yd³ |
| 16 | 0.59 yd³ |
| 18 | 0.67 yd³ |
| 27 | 1.00 yd³ |
| 32 | 1.19 yd³ |
| 48 | 1.78 yd³ |
| 54 | 2.00 yd³ |
| 72 | 2.67 yd³ |
Convert raised-bed volume to soil bags
Divide total cubic feet by the bag volume. A 32-cu-ft project would need 16 two-cu-ft bags or about 22 1.5-cu-ft bags after rounding up. If you have multiple beds, calculate the combined volume before deciding between bags and bulk.
Example: three 4 × 8 beds
At 12 inches deep, one 4 × 8 bed needs 32 cubic feet. Three beds need 96 cubic feet, or about 3.56 cubic yards. With 2-cu-ft bags, that is 48 bags before any settling allowance.
At only 9 inches deep, the same three beds need 72 cubic feet, or about 2.67 cubic yards. Changing the planned depth by three inches removes nearly one full cubic yard from the order.
Why actual bed volume may differ from the chart
- Nominal 4 × 8 dimensions may be slightly larger than the usable inside dimensions.
- The bed may already contain soil or lower-fill material.
- You may intentionally leave headspace below the top edge.
- Fresh mix may settle after watering.
- A sloped base can create variable depth.
That is why the raised bed soil volume chart is best for quick planning rather than final ordering.
Choose soil depth before buying material
Depth can have a bigger effect on the order than bag size. If you are not sure what depth makes sense for the bed design and crops, read the Raised Bed Soil Depth Guide first.
Common raised-bed volume mistakes
- Using inches directly in a feet-based formula.
- Forgetting to multiply by the number of beds.
- Using outside dimensions when bed walls are thick.
- Assuming the entire frame height will be filled with purchased soil.
- Rounding each bed separately and creating an excessive total allowance.
Frequently asked questions
How much soil is needed for a 4 × 8 raised bed?
At 12 inches deep, about 32 cubic feet or 1.19 cubic yards. At 6 inches deep, about 16 cubic feet.
How much soil is needed for a 3 × 6 bed?
At 12 inches deep, 18 cubic feet. At 18 inches deep, 27 cubic feet or one cubic yard.
How many cubic feet are in one cubic yard?
There are 27 cubic feet in one cubic yard.
Use the chart to compare designs, then enter the real inside measurements in the Raised Bed Soil Calculator before purchasing.
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