How Much Soil Does a Raised Bed Need?
Volume of a rectangular raised bed = Length × Width × Height. Since everything is measured in feet, you get cubic feet directly. Divide by 27 for cubic yards.
cubic feet = L (ft) × W (ft) × H (ft)
cubic yards = cubic feet ÷ 27Common Raised Bed Sizes — Soil Volume Table
| Bed size | Height 6 in | Height 12 in | Height 18 in |
|---|---|---|---|
| 4 × 4 ft | 0.30 yd³ | 0.59 yd³ | 0.89 yd³ |
| 4 × 8 ft | 0.59 yd³ | 1.19 yd³ | 1.78 yd³ |
| 4 × 12 ft | 0.89 yd³ | 1.78 yd³ | 2.67 yd³ |
| 3 × 6 ft | 0.33 yd³ | 0.67 yd³ | 1.00 yd³ |
| 6 × 10 ft | 1.11 yd³ | 2.22 yd³ | 3.33 yd³ |
Recommended Soil Mix Ratios
| Recipe | Topsoil | Compost | Amendment | Best for |
|---|---|---|---|---|
| Mel's Mix | 0% | 33% | 33% peat + 33% vermiculite | All vegetables |
| Budget mix | 60% | 30% | 10% perlite/coarse sand | Large beds |
| Premium blend | 40% | 40% | 20% perlite | Herbs, salads |
| Native + compost | 50% native | 50% | — | Budget fill beds |
Do not use 100% native yard soil — it compacts hard and drains poorly in raised beds. Always blend with compost or amendment.
Depth Requirements by Crop
| Vegetable/Herb | Minimum depth |
|---|---|
| Lettuce, radishes, herbs | 6 inches |
| Tomatoes, peppers, squash | 12 inches |
| Carrots, beets, parsnips | 12–18 inches |
| Potatoes | 12–18 inches |
| Corn (not typical in raised beds) | 24 inches |
Source: Utah State University Extension — Vegetable Planting Guide