How much soil and compost to fill a raised bed
Put in the size of your bed and choose a mix. You'll get the volume, how much topsoil and compost that is, and how many bags to buy.
Soil to buy
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How the sums work
The volume of a bed is its length × width × depth. A cubic metre is 1,000 litres, and a cubic foot is about 28 litres. The calculator adds the extra you choose for settling, because the soil in a new bed sinks as the compost in it breaks down and the air pockets close. Then it splits the total by the mix.
Topsoil is shown in tonnes as well as litres, because builders' merchants sell it by the bulk bag. A tonne of standard topsoil is about 0.67 cubic metres, according to the turf and topsoil supplier Rolawn, so a tonne bag fills less than a cubic metre. Damp or heavy soil weighs more, so check the supplier's figure.
Which mix to use
Half topsoil, half compost is a reliable all-round mix for vegetables on ordinary ground. University of Maryland Extension suggests compost and topsoil at 1 to 1 or 1 to 2 on top of heavy or compacted soil, which is the second option here. On paving or concrete, where roots can't reach the ground below, it suggests compost and a soil-free growing mix half and half, so choose all compost.
A bed on dug ground doesn't need to be deep: 20 to 30 cm is enough for most crops, since roots carry on into the soil below. Our guide to planning a raised bed covers sizes and layout.
Draw your beds to scale and fill them
VegLog's bed planner spaces every crop for you and warns you when plants are too close. Free for your first growing space.
