How to calculate soil for a raised bed
Cubic yards = Cubic feet ÷ 27
Worked example
A common 8 × 4 ft bed filled 12 in deep holds 8 × 4 × 1 = 32 cubic feet of soil. With 10% extra for settling that's about 35 cubic feet: 24 bags of 1.5 ft³, or 1.3 cubic yards if you buy in bulk.
Soil needed for common bed sizes
| Bed size | 6 in deep | 12 in deep | 18 in deep |
|---|---|---|---|
| 4 × 4 ft | 8 ft³ | 16 ft³ | 24 ft³ |
| 8 × 4 ft | 16 ft³ | 32 ft³ | 48 ft³ |
| 8 × 3 ft | 12 ft³ | 24 ft³ | 36 ft³ |
| 10 × 4 ft | 20 ft³ | 40 ft³ | 60 ft³ |
Figures are before the allowance for settling.
What to fill a raised bed with
A simple, reliable mix is about 60% screened topsoil and 40% compost. Topsoil gives structure and holds moisture, while compost adds nutrients and keeps the soil loose. Some gardeners use a third component such as coconut coir, peat or vermiculite for extra drainage.
For deep beds (over 18 in), you can fill the bottom third with logs, branches and leaves, a method sometimes called hugelkultur, to cut the amount of soil you need. Measure only the part you'll fill with soil.
Bags or bulk?
One cubic yard is 27 cubic feet, the same as 18 bags of 1.5 ft³. Once you need more than about a yard, bulk soil is usually much cheaper, but it has to be shoveled in by hand. Use the topsoil calculator for in-ground beds.
Frequently asked questions
How many bags of soil do I need for a 4 × 8 raised bed?
A 4 × 8 ft bed 12 in deep needs 32 cubic feet: about 22 bags of 1.5 ft³ or 16 bags of 2 ft³, plus a few extra for settling.
How deep should a raised bed be?
8–12 in suits most vegetables and flowers. Root crops like carrots and potatoes do best with 12–18 in.
Should I use potting mix in a raised bed?
Potting mix is designed for containers and drains very fast. For raised beds, a mix of topsoil and compost is cheaper and holds moisture better.
How many cubic feet are in a yard of soil?
27. A cubic yard of soil fills a 4 × 8 ft bed about 10 in deep.
Last reviewed 2026-11-14. Material weights are typical industry averages and vary by supplier, moisture and compaction.