CalculatorMulchHow much of each to fill a raised bed?
A raised bed filled with pure compost slumps by a third in a season. The ratio matters as much as the volume.
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How this works
Common raised-bed mixes
Shares by volume, not by weight.
| Mix | Topsoil | Compost | Aeration |
|---|---|---|---|
| General vegetable bed | 60% | 30% | 10% perlite or grit |
| Heavy-feeding beds | 50% | 40% | 10% perlite |
| Mediterranean or alpine | 50% | 20% | 30% grit |
| Container mix | 30% | 40% | 30% bark and perlite |
A bed of pure compost slumps by up to a third in one season and holds nutrients so strongly it can burn seedlings.
Frequently asked questions
Why not fill a raised bed with compost?
It has almost no mineral structure, so it decomposes and collapses, and it holds nutrients so strongly that it can burn seedlings in the first season. It belongs in a mix, not on its own.
Why allow twenty percent for settling?
Because a freshly filled bed settles substantially in the first few weeks, and topping it up later means a second small order at the worst price.