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SOIL & MATERIALS

How Much Soil Do I Need for a Raised Bed?

The useful number is the volume that still needs filling, not simply the outside size of the bed. Measure the usable inside dimensions and account for soil already present.

Measure the space that needs soil

Record inside length and width, then the remaining fill depth. Existing soil below or inside the frame changes how much new material is needed.

Soil choice also depends on the site below the bed. Extension guidance distinguishes beds over usable native soil from beds on hard, non-permeable surfaces. [1]

Calculate rectangular volume

Convert all three dimensions to compatible units, then multiply length × width × depth. Keep precision until the final display conversion.

Raised-bed example8 ft × 4 ft × 12 in
  1. Convert 12 inches to 1 foot.
  2. 8 × 4 × 1 = 32 cubic feet.
  3. 32 ÷ 27 ≈ 1.19 cubic yards.
  4. 32 × 28.316846592 ≈ 906 liters.

Translate volume into a purchase

For bags, divide the required volume by the volume printed on one bag and round the purchasing count up. For bulk material, check the supplier's selling increment.

Keep any buffer visible and optional. It can help with measurement variation or settling, but it should not replace measuring the actual empty depth.

Use this guide with Grownestia

Calculate your soil volume

Enter mixed units, compare cubic feet, cubic yards and liters, and estimate whole bags.

Sources

  1. University of Maryland Extension: Soil to Fill Raised BedsReviewed by Grownestia 2026-09-09