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.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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