Raised bed soil calculator

Fill one raised bed or a whole row of identical beds without over-ordering. Enter the internal dimensions and the number of beds.

Raised bed soil calculator

Everything is worked out in your browser — nothing is sent anywhere.

Length

Width

Length & width unit

Depth

Depth unit

Number of identical beds

Cubic feet: 32.00
Cubic yards: 1.19
Cubic metres: 0.91
Litres: 906

Roughly 43 standard 0.75 cu ft bags of soil or compost. Order about 5–10% extra to allow for settling.

Measure the inside, not the outside

Raised bed sides are often 1–2 inches thick, and timber sleepers can be much thicker. Measure the internal length and width, or you will order soil for wood you already own.

How deep does a raised bed need to be?

6 inches — salads, herbs and other shallow-rooted crops, if the bed sits on decent open soil.
10–12 inches — the usual choice for mixed vegetable growing.
18 inches or more — beds on a hard surface, or for deep-rooting crops such as parsnips and potatoes.

A practical fill mix

A reliable starting point is roughly 60% quality topsoil, 30% finished compost and 10% bulky material such as leaf mould or well-rotted manure. Very deep beds can be part-filled at the base with coarse organic matter, though that layer settles noticeably in the first year, so plan to top the bed up.

Worked example

Three beds, each 8 ft × 4 ft, filled 12 inches deep: 8 × 4 × 1 = 32 cubic feet per bed, so 96 cubic feet in total — about 3.6 cubic yards. At that volume a bulk delivery is almost always cheaper than bags.

Allow for settling

Fresh compost-heavy mixes can settle 10–15% in the first season. Fill beds slightly proud of the sides, water them in, and keep a little material back for topping up in spring.