How to fill a raised garden bed in Australia
The maths is straightforward: length × width × depth = volume in m³. A standard 2.4 m × 1.2 m bed at 300 mm deep needs 0.86 m³ — that's about 29 × 30 L bags, or a small bulk delivery from your landscape yard.
Bags vs bulk delivery — which is cheaper?
Bagged soil works well for one or two small beds. Above about 0.5 m³ (15–20 bags), bulk delivery from a landscape yard is significantly cheaper and you avoid lugging bags. Most yards sell garden and veggie mix by the cubic metre with a 0.5–1.0 m³ minimum. A cubic metre delivered typically costs $80–$150 depending on mix quality and location — compared to $150–$200+ in bags for the same volume.
What soil mix should I use?
- Premium veggie mix — high organic matter, good drainage, ideal for raised beds. Look for mixes with compost, coir and coarse sand.
- Garden / topsoil blend — heavier, better for in-ground beds being topped up or mixed with existing soil.
- Compost-heavy mix — great as an annual 50–75 mm top-dress to replenish nutrients rather than a full fill.
- Potting / container mix — lightweight and well-draining; good for pots but expensive for large raised beds.
Settling allowance
Freshly filled beds settle 10–20% over the first growing season as organic material breaks down. Fill to the brim when first planting — they'll settle to a workable level by season two. Top-dress annually with 50–75 mm of compost to keep levels up and feed the soil.
How many beds does a cubic metre fill?
At 300 mm depth, one cubic metre covers 3.33 m² of bed area — roughly one standard 2.4 × 1.2 m bed, or three 1.0 × 1.0 m square-foot garden frames.