How much soil for a 4×8 raised bed?
Quick Answer
A standard 4×8 foot raised bed filled 12 inches deep needs 32 cubic feet of soil — about 1.19 cubic yards. At 10 inches deep: 0.99 yd³. At 6 inches: 0.59 yd³. Most gardeners use a mix of topsoil, compost, and coarse vermiculite (Mel's Mix) rather than straight topsoil for better drainage and root development.
Quick Reference Table
| Fill depth | Soil needed for 4×8 raised bed |
|---|---|
| 6 inches | 16 cu ft / 0.59 yd³ |
| 8 inches | 21.3 cu ft / 0.79 yd³ |
| 10 inches | 26.7 cu ft / 0.99 yd³ |
| 12 inches | 32 cu ft / 1.19 yd³ |
| 16 inches | 42.7 cu ft / 1.58 yd³ |
| Bags needed (1 cu ft bags, 12") | 32 bags |
How to Calculate It Yourself
- 1
Calculate volume: 4 ft × 8 ft × depth (ft). At 12": 4 × 8 × 1 = 32 cubic feet.
- 2
Convert to cubic yards: 32 ÷ 27 = 1.19 yd³.
- 3
For Mel's Mix (recommended): ⅓ compost, ⅓ peat moss or coco coir, ⅓ coarse vermiculite.
- 4
At 12" deep, buy 11 cubic feet each of compost, peat, and vermiculite. Or order 1.2 yards of pre-blended raised bed mix.
Pro Tip
Never fill a raised bed with straight topsoil — it compacts badly and drains poorly. Blended "raised bed mix" from garden centers costs more but plants perform dramatically better. Budget $60–120 for a 4×8×12 fill with quality blended mix.
Assumptions to Check
Before ordering materials, confirm the dimensions, product coverage, waste factor, and local installation requirements for your project. Manufacturer coverage tables and local code rules can change the final quantity, especially for structural work, exterior projects, and irregular layouts.
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