Living Soil Volume Calculator and Bed Guide
Living Soil Calculator Australia
Before ordering living soil, compost, or amendments, it is essential to calculate how much volume you actually need. Garden beds, fabric pots, and raised systems are sold by physical dimensions, while soil is sold by volume (litres or cubic metres). Misjudging this can lead to under-ordering, excess cost, or inconsistent growing conditions.
This page helps you accurately estimate soil requirements for common garden beds and containers used in Australian home gardens, balconies, greenhouses, and commercial setups. It also helps you convert litres into bag quantities based on current Green Genius packaging sizes.
Living Soil Volume Calculator
This calculator estimates soil volume for rectangular beds, round pots, and known container volumes. Enter your dimensions in centimetres and select a bag size to see how many bags you will need.
Living Soil Volume Calculator
Common Bed Sizes and Soil Volumes
The table below shows estimated soil volumes for the most common raised bed and fabric bed sizes available in Australia. All depths are based on the standard 45 cm (1.5 ft) height used by Grassroots Fabric Beds, which are stocked at Green Genius. Volumes are calculated at a 90% fill factor to allow for a mulch or top-dressing layer.
| Common Name | Metric Dimensions (L × W × D) | Volume at 90% Fill | 20 L Bags Needed | 40 L Bags Needed |
|---|---|---|---|---|
| 2 × 4 bed | 115 × 55 × 45 cm | ~257 L | 13 | 7 |
| 3 × 3 bed | 85 × 85 × 45 cm | ~292 L | 15 | 8 |
| 4 × 4 bed | 115 × 115 × 45 cm | ~534 L | 27 | 14 |
| 4 × 8 bed | 115 × 245 × 45 cm | ~1,141 L | 58 | 29 |
These figures are based on the Grassroots Fabric Bed dimensions stocked at Green Genius. If your bed has different dimensions, use the calculator above to get an accurate estimate.
Understanding Living Soil Depth
Soil depth is one of the most important variables in any growing system. It directly affects root development, water retention, and the biological activity that makes living soil work. Getting the depth right is just as important as getting the total volume right.
For most annual vegetables and herbs, a minimum of 30 cm of living soil is recommended. This gives roots enough room to develop without restriction and allows the soil food web — bacteria, fungi, protozoa, and other organisms — to establish across multiple layers. Shallow beds of 15–20 cm can work for leafy greens and herbs, but they dry out faster and offer less biological buffering.
For larger plants, fruiting crops, and perennials, 45 cm or more is ideal. This is why the standard Grassroots Fabric Bed height of 45 cm (1.5 ft) is well suited to living soil systems. It provides enough depth for a structured soil profile: a lower zone for root exploration and moisture retention, and an upper zone for active microbial life and nutrient cycling.
When filling a bed for the first time, it is common for the soil to settle by 5–10% over the first few weeks as it is watered and microbial activity begins. This is normal. Filling to 90% of the bed height and reserving the top 10% for a mulch layer is a practical approach that accounts for this settling.
Soil Volume vs Bag Volume: What You Need to Know
Soil bags are sold by volume, but the stated volume on the bag refers to the loose, uncompacted material as it leaves the bag. Once soil is placed into a bed and watered, it will settle and compact slightly. This means the volume in the bag and the volume in your bed are not always identical.
As a general rule, add a 5–10% buffer to your calculated volume when ordering. For example, if your calculator result shows 500 L, ordering 550 L worth of product gives you a practical margin. The reference table above already applies a 90% fill factor, which accounts for this in most situations.
For very large installations — such as multiple 4 × 8 beds or commercial greenhouse setups — Green Genius stocks the RSO Potting Mix in bulk formats including pallet quantities (40 × 20 L bags), 1,000 L bulker bags, and loose cubic metre orders. Contact the team at support@greengenius.com.au to discuss bulk pricing and delivery options for large volumes.
Filling Fabric Pots with Living Soil
Fabric pots are a popular choice for living soil growers because they air-prune roots, prevent waterlogging, and allow the soil to breathe. The Grassroots Fabric Beds stocked at Green Genius are made from breathable fabric and are available in sizes from 2 × 4 ft (55 × 115 cm) through to 4 × 8 ft (115 × 245 cm).
When filling fabric pots or beds, keep the following in mind:
- Fill to approximately 90% of the bed height to allow for a mulch layer and to prevent soil spilling when watering.
- Moisten the soil as you fill rather than watering heavily after filling. This helps the soil settle evenly and avoids channelling.
- Fabric beds placed on hard surfaces such as concrete or pavers will drain freely. Ensure the surface can handle runoff, particularly during the establishment phase when watering frequency is higher.
- If stacking or layering different materials in a bed, calculate each layer separately using the calculator above and add the volumes together.
Filling Raised Garden Beds
Raised garden beds — whether timber, metal, or modular — follow the same volume principles as fabric beds. The key difference is that raised beds on soil can benefit from the native soil below, particularly for deep-rooted plants. In this case, you may choose to fill only the upper portion of the bed with living soil and allow roots to penetrate into the native ground below.
For beds placed directly on native soil, a common approach is to fill the lower third with a coarser drainage layer and the upper two-thirds with living soil. Use the calculator above to calculate the volume of the upper layer only, entering the depth of the living soil portion rather than the full bed height.
For beds on raised platforms, balconies, or impermeable surfaces, fill the entire bed depth with living soil or a combination of living soil and a drainage layer at the base. In these situations, accurate volume calculation is especially important because there is no native soil to supplement the growing medium.
Green Genius Living Soil Products
Green Genius stocks a curated range of living soil and potting products suited to Australian growing conditions. The following products are available in bag sizes compatible with the calculator above.
- HPO GRO-DIRT Full Spec — Available in 20 L and 40 L bags. A fully amended living soil designed for high-performance growing. Suited to growers who want a complete, ready-to-use medium.
- HPO GRO-DIRT Lite — Available in 20 L and 40 L bags. A lighter-weight living soil base for growers who prefer to customise their own amendment programme.
- RSO Potting Mix — Available in 20 L bags, 40-bag pallets, 1,000 L bulker bags, and bulk cubic metre orders. A versatile potting mix suited to a wide range of container and raised bed applications.
Browse the full Living Soil collection at Green Genius to see current stock, pricing, and availability.
Ordering and Delivery
Green Genius ships Australia-wide. Orders are dispatched within one business day of payment being received. Estimated delivery times are 1–2 business days for Brisbane and surrounding areas, 2–4 business days for other parts of Queensland, and 3–7 business days for other states and territories.
Shipping costs are calculated at checkout based on the weight and dimensions of your order. For large soil orders — particularly pallet quantities or bulker bags — please contact the team at support@greengenius.com.au before placing your order to confirm freight options and costs to your location.
If you have questions about which product is right for your setup, the Green Genius team is available to help. Visit the showroom in Brisbane or reach out via email.
Quick Soil Volume Table
This reference table provides approximate soil volumes for common Green Genius-compatible bed and pot sizes. Always confirm internal dimensions where available.
Raised Beds
| Bed Size | Depth | Volume (L) |
|---|---|---|
| 1.2 × 0.6 m | 20 cm | 144 L |
| 1.2 × 0.6 m | 30 cm | 216 L |
| 1.2 × 0.6 m | 40 cm | 288 L |
| 1.2 × 1.2 m | 20 cm | 288 L |
| 1.2 × 1.2 m | 30 cm | 432 L |
| 1.2 × 1.2 m | 40 cm | 576 L |
| 2.4 × 1.2 m | 20 cm | 576 L |
| 2.4 × 1.2 m | 30 cm | 864 L |
| 2.4 × 1.2 m | 40 cm | 1,152 L |
Common Fabric Pots (typical ranges)
| Pot Size | Approx Volume |
| Small fabric pot | 10–20 L |
| Medium fabric pot | 30–50 L |
| Large fabric pot | 70–100 L |
| Extra large pot | 100–200 L |
GrassRoots bed sizes and exact internal volumes should be confirmed against current product listings where available.
Choosing Soil Depth
Soil depth is one of the most important decisions in container growing. Rather than prescribing a single ideal depth, consider the following:
- Root depth requirements of your crop
- Total container height and usable volume
- Water-holding capacity in hot Australian climates
- Drainage and aeration balance
- Long-term reuse and soil biology stability
- Weight when fully saturated
- Structural load limits for balconies, decks, and shelving
- Irrigation method and distribution
Always consider the weight of wet soil before installing large beds on elevated structures. If unsure, seek structural advice before installation.
Build a Living Soil System
A living soil system is not a single product but a combination of functional components:
- Base growing medium
- Compost or worm castings
- Aeration materials
- Mineral inputs
- Organic nutrient sources
- Microbial inoculants
- Mulch layer
- Cover crops (where appropriate)
- Irrigation system
Explore related Green Genius collections:
- Living Soil
- Soil Amendments
- Composting
- OGS
- HPO
- GrassRoots Pots and Beds
- Blumat
- Irrigation
- Beneficial Microorganisms
Avoid overloading soil with unnecessary inputs. Follow product directions for all amendments.
Filling a New Fabric Bed
- Confirm final placement before filling
- Check drainage and floor protection
- Calculate required volume
- Pre-moisten dry base materials if required
- Mix components evenly if blending
- Fill in layers without excessive compaction
- Install irrigation system
- Apply mulch layer
- Allow soil to stabilise where required
Reusing and Re-Amending Living Soil
Living soil can often be reused across multiple growing cycles.
Key practices include:
- Removing large old root masses where appropriate
- Preserving soil structure and biology
- Adding compost to restore organic matter
- Topping up lost volume
- Testing when nutrient balance is uncertain
- Applying amendments only as directed
- Maintaining mulch cover
- Keeping irrigation consistent
Avoid unnecessary or repeated blind amendment applications.
Shop Living Soil in Brisbane
Green Genius offers a range of living soil, compost, and soil amendment products available in-store and online.
- Visit our Brisbane store for in-person advice
- Order online for Australia-wide delivery
- Explore living soil blends, compost, aeration materials, and amendments
- Contact us for help planning large garden bed orders
Frequently Asked Questions
How do I calculate how much soil I need for a raised garden bed?
Multiply the length, width, and depth of your bed in centimetres, then divide by 1,000 to get the volume in litres. For example, a bed that is 120 cm long, 60 cm wide, and 45 cm deep requires 120 × 60 × 45 ÷ 1,000 = 324 litres. Use the calculator at the top of this page to do this automatically and convert the result into bag quantities.
How many litres of soil does a 4 × 4 fabric bed need?
A Grassroots 4 × 4 fabric bed measures 115 × 115 × 45 cm. At a 90% fill factor, this requires approximately 534 litres of soil, or around 27 bags of 20 L product or 14 bags of 40 L product.
How many litres of soil does a 4 × 8 fabric bed need?
A Grassroots 4 × 8 fabric bed measures 115 × 245 × 45 cm. At a 90% fill factor, this requires approximately 1,141 litres of soil. This is best ordered as a pallet or bulker bag quantity. Contact Green Genius to discuss bulk options.
How many litres of soil does a 4 × 2 fabric bed need?
A Grassroots 2 × 4 fabric bed measures 55 × 115 × 45 cm. At a 90% fill factor, this requires approximately 257 litres, or around 13 bags of 20 L product or 7 bags of 40 L product.
What is living soil depth?
Living soil depth refers to the vertical measurement of the soil layer in a bed or container. A minimum of 30 cm is recommended for most vegetable crops. Deeper beds of 45 cm or more support more complex root systems and a more diverse soil food web, which is the foundation of a living soil approach.
Can I use this calculator for fabric pots?
Yes. Select "Round Pot" for circular fabric pots and enter the diameter and depth. For rectangular fabric beds, use "Rectangular Bed" and enter the internal dimensions. The Grassroots Fabric Beds stocked at Green Genius are rectangular, so use the rectangular option for those.
Does Green Genius ship soil to all states?
Yes. Green Genius ships Australia-wide. Delivery times and costs vary by location and are calculated at checkout. For large or bulk orders, contact the team before ordering to confirm freight arrangements.