How It Works
The calculator uses a straightforward volume formula, then converts to cost based on your soil type and purchase method:
- Volume:Length (ft) × Width (ft) × Depth (in ÷ 12) = cubic feet per bed.
- Total:Cubic feet per bed × number of beds = total cubic feet.
- Cubic yards:Total cubic feet ÷ 27 = cubic yards (for bulk orders).
- Bags:Total cubic feet ÷ 1.5 cu ft per bag = number of bags (rounded up).
- Bottom fill:If enabled, reduces soil volume by 27% (the midpoint of 25–30%).
Bags vs Bulk: Cost Comparison
The break-even point depends on your bed size. Here's how common raised bed sizes compare using garden mix pricing:
| Bed Size | Depth | Cu Ft | Bags Cost | Bulk Cost | Savings |
|---|---|---|---|---|---|
| 4 × 4 ft | 12" | 16 | $66–80 | $24–33 | ~$35 |
| 4 × 8 ft | 12" | 32 | $132–160 | $47–65 | ~$80 |
| 4 × 8 ft | 6" | 16 | $66–80 | $24–33 | ~$35 |
| 3 × 6 ft | 12" | 18 | $72–96 | $27–37 | ~$40 |
| 2 × 8 ft | 10" | 13.3 | $54–72 | $20–27 | ~$30 |
Rule of thumb:bulk is almost always cheaper per cubic foot — but delivery fees ($50–150) only make sense once you need roughly 2+ cubic yards. For a single small bed, bags may be more practical.
Best Soil Mix for Raised Beds
The classic raised bed recipe is often called "Mel's Mix" (from Square Foot Gardening):
- 1/3 topsoil or peat moss— structure and moisture retention
- 1/3 compost(blended from multiple sources) — nutrients and microbiology
- 1/3 coarse vermiculite or perlite— drainage and aeration
If you're buying pre-mixed "raised bed soil," it usually contains a similar blend. Budget option: topsoil + compost at a 60/40 ratio works well for most vegetables.
FAQ
Is bulk soil always cheaper than bags?
Per cubic foot, yes. But bulk delivery typically costs $50–150 on top of the soil price. For a single 4×4 bed, bags might cost the same or less after delivery. For two or more beds, bulk almost always wins.
How much does Hügelkultur bottom fill actually save?
Filling the bottom 25–30% of a 12-inch deep bed with logs, branches, leaves, or cardboard displaces that much soil. On a 4×8 bed, that saves roughly 8–10 cubic feet of soil — about $40–60 in garden mix. It also improves drainage and feeds the soil as it decomposes.
How deep should a raised bed be for vegetables?
Most vegetables thrive in 10–12 inches of soil. Shallow-rooted crops (lettuce, herbs, strawberries) do fine in 6 inches. Root vegetables like carrots and parsnips need at least 12 inches.
Should I line the bottom of my raised bed?
Landscape fabric on the bottom prevents weeds from growing up but lets water drain. Avoid plastic liners — they trap water and cause root rot. Hardware cloth (1/2" mesh) keeps burrowing animals out if that's a concern.
Related Tools & Guides
- Soil Volume Calculator— calculate volume for any shape bed (circular, L-shaped, etc.)
- How to Fill a Raised Bed— step-by-step layering guide
- How Much Soil for a 4×8 Raised Bed— detailed breakdown with cost estimates
Prices shown are approximate 2026 U.S. averages and may vary significantly by region, retailer, and market conditions. Always get local quotes for accurate pricing.