How Much Soil Do I Need?
Enter your raised bed or garden bed dimensions to calculate exactly how many bags of soil to buy — in cubic feet, cubic yards, and bag count. Works for any size raised bed, planter, or in-ground garden.
How to Calculate Soil for a Raised Bed
The formula is straightforward: Length (ft) × Width (ft) × Depth (ft) = Cubic Feet. Convert depth from inches to feet by dividing by 12. Divide cubic feet by 27 to get cubic yards. Then divide by your bag size to get bag count — and add 10% for settling.
Example — Standard 4×8 raised bed at 12 inches deep: 4 × 8 × 1 = 32 cubic feet. With 10% buffer = 35.2 cubic feet. At 1.5 cu ft per bag, that's 24 bags. At bulk pricing (~$40–$60 per cubic yard), the same volume costs significantly less than bags at $8–$12 each.
Soil settles 10–20% after watering, especially with fluffy mixes high in peat or coco coir. Build in that buffer now rather than topping off after the first rain.
How Deep Should a Raised Bed Be?
| Crop Type | Minimum Depth | Recommended |
|---|---|---|
| Lettuce, spinach, herbs | 6 inches | 8 inches |
| Tomatoes, peppers, squash | 12 inches | 18 inches |
| Carrots, beets, parsnips | 12 inches | 18–24 inches |
| Potatoes | 12 inches | 18 inches |
| Most vegetables (general) | 12 inches | 12–18 inches |
| Perennial flowers / shrubs | 12 inches | 18 inches |
Most vegetable gardens do well at 12 inches of quality raised bed mix. Root crops like carrots and parsnips need 18 inches to develop properly — shorter beds limit root length and produce stunted, forked vegetables. If you're building on hard clay or compacted soil, add 2–4 extra inches to compensate for limited drainage below.
Soil Needed — Quick Reference
| Bed Size | 12" Deep (cu ft) | 12" Deep (bags, 1.5 cu ft) | 18" Deep (bags, 1.5 cu ft) |
|---|---|---|---|
| 2×4 ft | 8 cu ft | 6 bags | 9 bags |
| 4×4 ft | 16 cu ft | 12 bags | 18 bags |
| 4×8 ft | 32 cu ft | 24 bags | 35 bags |
| 4×12 ft | 48 cu ft | 35 bags | 53 bags |
| 4×16 ft | 64 cu ft | 47 bags | 71 bags |
| 8×8 ft | 64 cu ft | 47 bags | 71 bags |
All figures include a 10% settling buffer. For beds requiring 2+ cubic yards, contact a local garden center or landscape supplier for bulk soil delivery — it's almost always 30–50% cheaper than bagged.
Bags vs. Bulk Soil Cost
| Volume Needed | Bagged Cost (1.5 cu ft @ $9) | Bulk Cost (incl. delivery) | Savings with Bulk |
|---|---|---|---|
| 16 cu ft (4×4 bed) | ~$96 | Not practical | — |
| 32 cu ft (4×8 bed) | ~$192 | $100–$160 | $30–$90 |
| 54 cu ft (1 cu yd) | ~$324 | $60–$120 | $200+ |
| 108 cu ft (2 cu yd) | ~$648 | $120–$200 | $450+ |
Bulk makes sense at roughly 1 cubic yard or more — that's a standard 4×8 bed at 12 inches deep plus some extra. Below that, bags are perfectly practical and give you more control over soil mix type.