Raised Bed Soil Calculator
Fill volume for one or more raised beds, split into topsoil, compost and amendments by the parts you choose, with whole bags per component from your bag sizes.
How much of each ingredient to buy for the beds — in bags and in bulk — from your own mix recipe rather than a fixed one.
Example: Two 2.4 × 1.2 m beds filled 40 cm deep take 2,304 L. At 60 : 30 : 10 topsoil : compost : perlite that is 1,382 / 691 / 230 L — 35, 18 and 6 bags of 40 L.
The box sets the volume.
Your recipe splits it.
Fill depth versus bed height, how parts become litres and bags, and why no mix is prescribed.
Fill volume
Each bed is length × width × the depth you will actually fill — usually a little less than the side height so water and mulch have somewhere to go — times how many identical beds you have. The depth is entered in inches or centimetres and converted before multiplying; volumes are given in cubic feet or litres for bags and in cubic yards or cubic metres for bulk delivery. Beds with a gravel or log base (hügelkultur) should be entered with the soil depth only.
Parts and bags
The mix is given as parts by volume — 60 : 30 : 10, 1 : 1 : 1, or any numbers you like; each component gets its share of the total in proportion. Bags are counted per component from the bag size printed on that product (they differ: compost, perlite and topsoil rarely come in the same bag), rounded up to whole bags. A waste allowance, if you use one, is applied before the split.
Why no recipe is given
Raised-bed mixes vary with what is being grown, the climate, drainage, the local topsoil and what is affordable nearby; nurseries, extension services and growers all publish different ones. The page carries a labelled sample only so it has something to show, and the parts are yours to set. Note also that loose fill settles after the first waterings — often noticeably — so the figures are the volume as filled; top up later or fill slightly proud.
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SOURCES
Last reviewed 19 September 2026. How results are checked: How we verify.