How to use this calculator
Start by selecting whether your raised bed is rectangular or round. Enter the length and width for rectangular beds, or the diameter for round beds, in feet. Then enter the depth in inches. If you are filling more than one bed with the same dimensions, set the number of beds accordingly and the calculator will multiply the volume for you.
Choose between a standard soil mix of 60% topsoil, 30% compost, and 10% amendments, or Mel's Mix which uses equal parts compost, peat moss, and vermiculite. Click Calculate to see the total volume in cubic feet and cubic yards, how many bags you would need, a breakdown by ingredient, and an estimated cost for bulk delivery.
Why soil depth matters for raised beds
The depth of soil in your raised bed directly affects what you can grow and how well it performs. Shallow beds of 6 to 8 inches work for herbs, lettuce, and radishes, but anything with a deeper root system will struggle. Tomatoes, peppers, and squash need at least 12 inches, and root vegetables like carrots and parsnips do best with 18 inches or more.
Deeper beds also hold moisture longer between waterings and give roots more room to spread, which means healthier plants and better yields. If your bed sits on concrete or very compacted soil, the depth of the bed is all the growing space your plants will get, so err on the deeper side.