Raised Bed Soil Calculator
Calculate soil mix volume to fill a raised garden bed from length, width, and depth.
Returns cubic feet and yards with bag count for 1.5 and 2 cu ft bags.
Raised garden bed soil volume is the cubic footage (or cubic yards) of growing medium needed to fill a new bed. Ordering too little leaves beds under-filled; too much wastes money on expensive bagged or bulk soil.
Volume formula: Volume = Length × Width × Depth (Result in cubic feet if dimensions in feet; cubic inches ÷ 1,728 = cubic feet)
Cubic feet to cubic yards: Cubic Yards = Cubic Feet ÷ 27
(1 cubic yard = 3ft × 3ft × 3ft = 27 cubic feet; bulk soil and mulch are typically sold by the cubic yard)
Bags of bagged soil: Bags needed = Cubic Feet ÷ Volume per Bag Common bag sizes: 1 cubic foot, 1.5 cubic feet, 2 cubic feet.
What each variable means:
- Depth — the most important dimension; raised beds are only effective if deep enough for root systems:
- Lettuce, herbs, radishes: 6 inches minimum
- Most vegetables (tomatoes, peppers, carrots): 12 inches
- Deep-rooting vegetables (parsnips, potatoes): 18 inches
- Fill composition — a standard Mel’s Mix (Square Foot Gardening) uses: 1/3 compost + 1/3 peat moss/coco coir + 1/3 coarse vermiculite; never fill entirely with native soil (too dense)
- Settling allowance — fresh raised bed soil settles 10–20% in the first season; overfill by that margin or top-dress annually with compost
Reference: soil volume for common bed sizes:
| Bed Size | 6" depth | 12" depth | 18" depth |
|---|---|---|---|
| 4×4 ft | 8 cu ft | 16 cu ft | 24 cu ft |
| 4×8 ft | 16 cu ft | 32 cu ft | 48 cu ft |
| 4×12 ft | 24 cu ft | 48 cu ft | 72 cu ft |
| 4×16 ft | 32 cu ft | 64 cu ft | 96 cu ft |
Worked example: Two raised beds, each 4 ft × 8 ft × 12 inches deep.
- Volume per bed = 4 × 8 × (12÷12) = 4 × 8 × 1 = 32 cubic feet
- Total for two beds = 64 cubic feet
- In cubic yards = 64 ÷ 27 = 2.37 cubic yards → order 2.5 yards (adds settling buffer)
- Alternatively: 64 ÷ 2 = 32 bags of 2-cubic-foot bagged mix
Bulk delivery (2.5 cubic yards) typically costs $80–$150 plus delivery; the same volume in bagged soil costs $320–$480 at retail — bulk is almost always more economical for two or more large beds.