How much soil do I need for a raised bed?
A 4 x 8 ft raised bed 12 inches deep holds 32 cubic feet of soil: about 22 bags of 1.5 cu ft or 16 bags of 2 cu ft, plus about 10% extra for settling.
A raised bed holds its length × width × depth in feet. The table shows the exact volume; buy roughly 10% more, because soil settles once it’s watered.
| Bed | Soil | Bags of 1.5 cu ft | Bags of 2 cu ft | Cubic yards |
|---|---|---|---|---|
| 2 x 4 ft, 10 in deep | 6.7 cu ft | 5 bags | 4 bags | 0.25 |
| 3 x 6 ft, 12 in deep | 18 cu ft | 12 bags | 9 bags | 0.67 |
| 4 x 4 ft, 12 in deep | 16 cu ft | 11 bags | 8 bags | 0.59 |
| 4 x 8 ft, 12 in deep | 32 cu ft | 22 bags | 16 bags | 1.19 |
| 4 x 8 ft, 18 in deep | 48 cu ft | 32 bags | 24 bags | 1.78 |
| 4 x 12 ft, 12 in deep | 48 cu ft | 32 bags | 24 bags | 1.78 |
What to fill it with
Bagged “raised bed” or “garden” soil is a ready mix. A common blend if you mix your own is about 60% topsoil, 30% compost and 10% something airy like perlite or bark. For tall beds, filling the bottom third with logs, branches or leaves (sometimes called hugelkultur) saves soil.
For several beds, bulk soil by the cubic yard is usually much cheaper than bags: one cubic yard is 27 cubic feet, enough for a 4 x 8 bed about 10 inches deep.