Your Bed Dimensions
Tip: Keep width ≤ 1.2m so you can reach the centre from either side.
Recommended minimum: 30cm for most vegetables.
Your Results
Based on ~$80/m³ for quality raised bed mix. Prices vary by supplier and location. Look for mixes labelled “veggie mix” or “raised bed mix.”
Plant Capacity for Your Bed
Needs staking; 1-2 per m²
Dense planting; 12-16 per m²
Needs 30cm depth; ~50 per m²
Large plants; 3-4 per m²
Sprawling; 1 per 2 m²
On trellis; ~20 per m²
Similar to tomato; 3-4 per m²
Can grow densely; 16 per m²
Grid planting; ~30 per m²
Long harvest window; 4-6 per m²
Plant counts are theoretical maximums. In practice, allow extra space for air circulation and companion plants. Use our full spacing guide for 30+ crops.
Your Bed, Drawn to Scale
Pick a crop to see your bed laid out at its real spacing. This is the view you live in once you start planning inside Plant Planner.
A tomato bed, 2.4m × 1.2m, drawn to scale · about 7 plants at 50cm × 80cm spacing.
From the makers
Plan Your Entire Garden, Free
The calculator gives you soil and plant counts, Plant Planner goes further with a 12-month planting calendar, companion-optimised layouts, family consumption estimates, and email reminders.
How Much Soil Do You Need?
Calculating Soil Volume
The formula is simple: Length × Width × Height = Volume in m³. Multiply by 1000 to get litres. For a standard 2.4m × 1.2m × 0.3m raised bed, that's 2.4 × 1.2 × 0.3 = 0.864 m³, or 864 litres.
Always buy around 10-15% extra to account for soil settling over the first few months. Raised bed soil compresses as it settles and as organic matter breaks down. Top up each season with 5-8cm of fresh compost.
What Soil to Use
Garden centres sell premixed “raised bed mix” or “veggie mix.” The ideal mix is approximately 60% topsoil, 30% compost, and 10% coarse material (perlite, coarse sand, or wood chip) for drainage.
Avoid heavy clay soils, they compact in raised beds and inhibit root growth. Never use straight compost, which is too rich and can burn roots. For deep beds, you can fill the bottom 15cm with rough organic material like straw or wood chip (Hügelkultur method) and top with quality veggie mix.
Raised Bed Depth Guide
| Depth | Best for | Notes |
|---|---|---|
| 15-20cm | Herbs, lettuce, radish, microgreens | Minimum depth for shallow-rooted plants only. Dries out quickly. |
| 20-30cm | Most leafy greens, silverbeet, beans | Good for most crops except deep-rooted root vegetables. |
| 30cm (recommended) | Tomatoes, capsicum, carrots, beetroot, broccoli | The ideal all-purpose depth. Suits the vast majority of vegetables. |
| 40-45cm | Parsnip, large pumpkin, deep potato, accessibility | Best for deep root veg and raised beds where you need to reach from a seat or wheelchair. |
| 60cm+ | Potatoes, asparagus, artichokes, specialty crops | Deep beds for perennial crops and maximum productivity. High soil cost. |
How Many Plants Per Raised Bed?
The number of plants per raised bed depends entirely on the crop's spacing requirements. Use the calculator above for your exact bed size, or use these rough rules of thumb for a standard 1.2m × 2.4m bed (approximately 2.9 m²):
Tomatoes
5-7 plants
Broccoli
7-10 plants
Lettuce
27-38 plants
Carrots
126-180 plants
Garlic
67-96 cloves
Beans
45-64 plants
Basil
40-57 plants
Zucchini
2-3 plants
Plan Your Entire Garden, Free
The calculator above gives you soil and plant counts, but Plant Planner goes further with a 12-month planting calendar, companion-optimised bed layouts, family consumption estimates, and email reminders for every task.
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Frequently Asked Questions
How much soil do I need for a raised garden bed?
Multiply your bed length × width × height to get the cubic metres, then multiply by 1000 to convert to litres. For example, a standard 2.4m × 1.2m × 0.3m raised bed needs 864 litres of soil. Use a quality raised bed mix with compost, topsoil, and some coarse material for drainage.
How deep should a raised garden bed be?
30cm (300mm) is the ideal minimum depth for most vegetables. This accommodates most root vegetables like carrots and beetroot. 20cm works for shallow-rooted crops like lettuce, herbs, and radish. If building on concrete or a hard surface, go 40-45cm to give roots maximum room. Deeper beds also insulate roots better against temperature extremes.
How many tomato plants fit in a 4x8 bed (120cm x 240cm)?
A 120cm × 240cm raised bed (about 2.9 square metres) comfortably fits 5-7 tomato plants, depending on the variety. Indeterminate (vining) tomatoes need 50-60cm spacing and should be staked or caged, so stay nearer 5 in this bed size. Determinate (bush) tomatoes can be planted 45cm apart, allowing up to 7. Avoid overcrowding tomatoes as it reduces air circulation and increases disease risk.
What is the best size for a raised garden bed?
The most practical raised bed size is 1.2m wide by 2.4m long (4 foot by 8 foot). The 1.2m width is critical, it means you can reach the centre from either side without stepping in the bed, avoiding soil compaction. Length can vary based on space. For height, 30cm is the standard minimum; 45cm is better for root vegetables and accessibility.