How to use this raised bed soil calculator
- Measure the inside length and width of the bed.
- Enter the soil depth: 6–8 inches for shallow-rooted crops, 12 inches or more for most vegetables.
- Add a little extra: new soil settles by 10–20% after watering.
Example
Two 4 × 8 ft raised beds filled 12 inches deep need 64 cu ft of soil (2.37 cu yd). That is 43 bags of 1.5 cu ft or 33 bags of 2 cu ft, so buying a cubic yard in bulk could be cheaper.
What to know before you buy
How deep should a raised bed be?
Most vegetables grow well in 10–12 inches of good soil. Root crops such as carrots and potatoes prefer 12–18 inches. Beds placed on concrete or poor soil should be deeper, since roots cannot grow into the ground below.
Bulk or bagged soil?
A cubic yard of bulk soil equals 27 cubic feet, or 18 bags of 1.5 cu ft. For more than one or two beds, bulk delivery is usually much cheaper, even with a delivery fee.
Soil for common raised bed sizes
| Bed | Soil needed | Cubic yards | 1.5 cu ft bags |
|---|---|---|---|
| 4 × 4 ft, 6 in deep | 8 cu ft | 0.3 cu yd | 6 |
| 4 × 4 ft, 12 in deep | 16 cu ft | 0.59 cu yd | 11 |
| 3 × 6 ft, 12 in deep | 18 cu ft | 0.67 cu yd | 13 |
| 4 × 8 ft, 12 in deep | 32 cu ft | 1.19 cu yd | 22 |
| 4 × 8 ft, 18 in deep | 48 cu ft | 1.78 cu yd | 33 |
| 4 × 12 ft, 12 in deep | 48 cu ft | 1.78 cu yd | 33 |
Formula
Volume = length × width × depth × number of beds.
Tips from the pros
- Fill the bottom of deep beds with logs and branches (hugelkultur) to save on soil.
- Use a mix of about 60% topsoil and 40% compost.
- Top up with 1–2 inches of compost each season as the soil settles.
Common mistakes to avoid
- Filling beds with pure bagged potting mix, which dries out and is expensive at this scale.
- Not accounting for settling: new soil can drop 10–20% in the first season.
Frequently asked questions
How much soil for a 4×8 raised bed?
At 12 inches deep, 32 cubic feet, or about 1.2 cubic yards.
What soil should I use in a raised bed?
A mix of roughly 60% topsoil and 40% compost is a common, affordable choice.
How many bags of soil for a 4x4 raised bed?
At 12 inches deep, a 4 × 4 ft bed needs 16 cubic feet: about 11 bags of 1.5 cu ft or 8 bags of 2 cu ft.
Can I use topsoil alone in a raised bed?
It works, but mixing in compost improves drainage, fertility and structure.