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.
Garden bed volume calculator — frequently asked questions
How do I calculate the volume of a raised garden bed?
For a rectangular bed, multiply length × width × height (all in metres). For a round bed, use π × radius² × height. The calculator does both automatically. Just make sure all measurements are in the same unit before you enter them.
How much does it cost to fill a raised garden bed in Australia?
A standard 2.4 m × 1.2 m × 0.3 m raised bed holds about 0.86 m³. At $80 per cubic metre for bulk soil mix, that's around $70 for the soil alone before delivery. Using bagged premium potting mix from Bunnings, the same volume costs $150–$200.
Should I fill my raised bed with potting mix or garden soil?
Neither on its own — a blend works best. A mix of 60% quality loam, 30% compost and 10% coarse sand gives good drainage and nutrients. Pure potting mix dries out fast in Queensland summers and can be expensive for large beds. Pure garden soil compacts too much.
What material should I use for a raised garden bed in Queensland?
Hardwood sleepers (treated pine or hardwood) are the most common choice — durable, affordable and widely available. Galvanised steel beds are increasingly popular for their longevity and clean look. Avoid treated pine rated below H4 for vegetable gardens as the preservatives can leach into soil over time.
Do I need to line the bottom of a raised garden bed?
A layer of cardboard at the base suppresses weeds and breaks down within a season. Hardware cloth or mesh is worth adding if you have bandicoots, rats or other burrowing pests — common in many parts of Queensland and regional Australia.