Raised Bed Soil Calculator
Calculate how much soil and compost you need to fill a raised garden bed, with mix breakdowns.
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How to use this calculator
Multiply the bed dimensions to get total volume. The soil mix type determines how that volume is split between topsoil, compost, and perlite.
- 1
Measure your raised bed length and width in metres.
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Enter the bed depth in centimetres.
- 3
Select your preferred soil mix type.
- 4
Read off the total volume, litre requirements, and bag counts for each component.
Frequently asked questions
What is Mel's Mix?
Mel Bartholomew's Square Foot Gardening mix is 60% compost, 30% vermiculite, and 10% peat moss. It is lightweight, drains well, and retains moisture — ideal for raised beds.
How deep should a raised bed be?
A minimum of 15–20 cm suits most flowers and shallow vegetables. Root vegetables like carrots and parsnips need 30–45 cm. Deeper beds retain more moisture and give roots more room to grow.
Can I use garden soil in a raised bed?
Native garden soil tends to compact, which inhibits drainage and root growth. A purpose-made mix with compost improves structure, drainage, and fertility.
Raised Bed Soil Calculator — Volume, Litres & Bags
Choosing a Soil Mix for Raised Beds
The most popular options are 100% quality topsoil, a 50/50 blend of topsoil and compost, and Mel's Mix (60% compost / 30% vermiculite / 10% peat). Mel's Mix produces excellent results in square-foot gardening beds because it retains moisture without waterlogging.
How Much Soil Do Raised Beds Need?
A standard 1.2 × 0.6 m bed filled to 30 cm depth requires about 216 litres of soil mix — roughly six 40-litre bags. Larger or deeper beds quickly add up, so bulk delivery is often more economical than buying individual bags.
Saving Money on Raised Bed Soil
Compare the price per litre when choosing between bagged and bulk soil. Home-made compost is free and improves any mix. Top up with a 5 cm layer of fresh compost each year to replenish nutrients and maintain soil structure.
Learn more from an authoritative source:
WikipediaMulch Calculator
Calculate how many cubic yards or cubic metres of mulch you need for a garden bed, plus bags required.
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Calculate exactly how much grass seed you need based on lawn area, grass type, and seeding purpose.
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Calculate how many plants fit in a garden bed using square grid or triangular offset planting patterns.
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Calculate how much water your garden needs per week based on plant type, climate, and recent rainfall.
Results are estimates for informational purposes only and do not constitute professional financial, medical, legal, or technical advice. Read full disclaimer →