Raised Bed Soil Calculator
Calculate soil mix volume to fill a raised garden bed from length, width, and depth.
Returns cubic feet, yards, litres, bag counts, and the weight to move.
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 is 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
As a rough US guide in 2025, bulk raised-bed mix runs $30 to $60 a cubic yard delivered, against $4 to $8 for a 2 cubic foot bag. That bag price works out at $54 to $108 a yard once you have bought enough bags to fill one, so bulk wins on anything over about a cubic yard. Prices move a long way by region and season, so treat these as a starting point rather than a quote.
A note on weight. Raised bed mix is a peat or coir blend and runs about 40 lb per cubic foot, which is 640 kg per cubic metre. That is roughly half what garden loam weighs, and it matters: a 4 by 8 foot bed at 12 inches deep is 32 cubic feet, so about 1,280 lb (580 kg) of material to move by wheelbarrow. Do not let anyone talk you into filling a raised bed with topsoil, both for that reason and because it compacts and drains badly once it is boxed in.
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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