Raised bed soil calculator

How we worked it out

Updated as you change the numbers.

1. Volume of one bed = length × width × depth = 8 ft × 4 ft × 1 ft (12 in) = 32 cu ft.
2. Add 15% for settling: 32 × 1.15 = 36.8 cu ft.
3. Bags = 36.8 ÷ 1.5 cu ft = 24.53, rounded up to 25 bags.

Method and assumptions

The volume of a raised bed is its inside length × inside width × soil depth. The calculator adds your settling allowance, then rounds up to whole bags. For a recipe, each ingredient is worked out and rounded up on its own, because you buy them separately.

Bag sizes on garden soil are printed in cubic feet or quarts (1 cu ft ≈ 25.7 dry quarts) or liters (1 cu ft ≈ 28.3 L).

Tips

• Use inside measurements: with 2 in thick boards, an 8 × 4 ft bed is about 7.7 × 3.7 ft inside.
• For a tall bed, you can fill the bottom third with logs, branches or leaves and save soil.
• Plain topsoil or garden soil from the ground compacts in a bed. Most growers mix in plenty of compost.

Questions

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