"How much soil do I need?" is the first question almost everyone asks when they build a raised bed, and it is easy to get wrong.
11 inches deep (two 2×6 boards): about 29 cubic feet, or 34 cubic feet with settling, roughly 1.25 cubic yards.
Raised bed soil is a simple volume calculation.
These figures are before the settling allowance.
Depth has the biggest effect on how much soil you buy, so it is worth getting right rather than defaulting to the tallest bed you can build.
Plain topsoil on its own packs down in a raised bed, and bagged potting mix on its own is light, expensive and dries out fast.
Tall beds can swallow several cubic yards of soil.
Step-by-step advice, charts and free garden calculators at Garden Voila.