GardenCalc

Soil Calculator

Work out exactly how much soil, compost or topsoil you need for your garden bed, raised bed or planting area. No guesswork, no wasted bags.

Calculate Your Soil

Enter your bed dimensions and fill depth — we'll tell you the volume and how many bags to buy.

Your Results

Volume
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Volume
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Litres
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25-Litre Bags
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40-Litre Bags
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How Much Soil Do I Need?

This free soil calculator works out exactly how much soil, compost or topsoil you need to fill a raised bed, garden bed or any planting area. Enter your dimensions in metres or feet, set the fill depth in centimetres or inches, and get an instant answer in cubic metres, cubic feet, litres and number of bags.

Stop buying too many bags and hauling them back, or running short halfway through a project. Get the right amount first time.

Recommended Soil Depths by Use

Not sure how deep to fill? Here are the recommended depths for common garden projects.

Project Depth (cm) Depth (inches) Notes
Raised bed (vegetables) 25–30 10–12 Deep enough for most crops
Raised bed (root veg) 30–45 12–18 Carrots, parsnips, potatoes
Flower bed / border 15–20 6–8 Standard bedding plants
Top-dressing existing bed 5–10 2–4 Compost layer to refresh soil
Lawn levelling / top soil 2–5 1–2 Thin layer for levelling
Container / planter 20–40 8–16 Depends on container size

Frequently Asked Questions

How much soil do I need for a raised bed?
For a standard 1.2m × 2.4m (4ft × 8ft) raised bed filled to 30cm (12 inches) deep, you need approximately 0.86 cubic metres — that's around 860 litres, or roughly 34 bags of 25-litre compost. Use the calculator above with your exact dimensions to get a precise figure.
How many bags of topsoil do I need?
It depends on the area and depth. As a quick guide: one 25-litre bag covers about 0.25 square metres at 10cm deep. For larger projects, a 40-litre bag is more cost-effective. Enter your dimensions into the calculator and it will give you the exact bag count for both 25L and 40L sizes.
What is the difference between topsoil and compost?
Topsoil is natural soil that has been screened to remove stones and debris — it provides bulk and structure. Compost is decomposed organic matter rich in nutrients that feeds your plants. For filling raised beds, most gardeners use a mix of about 60% topsoil and 40% compost. For refreshing existing beds, a 5–10cm layer of pure compost works well. Both are measured the same way by volume, so this calculator works for either.
How deep should garden soil be?
Most vegetables and flowers need at least 15–20cm (6–8 inches) of good soil. Root vegetables like carrots and parsnips need 30cm (12 inches) or more. For raised beds, 25–30cm (10–12 inches) is the sweet spot — deep enough for nearly all plants without using excessive amounts of soil. See the depth guide table above for specific recommendations.