Calculating Soil Volume for Raised Beds with Existing Compost and Straw

You have two 4×4 ft beds and two 4×8 ft beds, each 8 inches deep. Currently, each contains about 6 inches of straw and 6 inches of compost (total 12 inches—overflowing). You want to know how much additional soil to add.

Volume Calculations

• Each 4×4×8″ bed needs ~10.5 cubic feet if empty.
• Each 4×8×8″ bed needs ~21 cubic feet if empty.

Adjust for Existing Material

Since beds are already overfilled with compost and straw, you likely don’t need more soil—just mix and settle the existing material. If you want a specific soil blend, remove some compost/straw first.