Raised-bed soil blend — split a contained bed volume into topsoil and compost by yards and bags

A raised bed is a contained volume — length × width × depth, no compaction. The calculator splits it into per-component yards AND bags: a 4×8×1 ft bed (32 ft³ = 1.19 yd³) in a 50/50 blend is 0.59 yd³ (≈16 bags) each of topsoil and compost. Fill, wet, then top off ~10% for settling.

What this diagram shows

A raised-bed soil blend broken into its components. A 4-by-8-by-1-foot bed is a contained volume with no compaction subtraction: 4 times 8 times 1 is 32 cubic feet, which divided by 27 is 1.19 cubic yards. A 50/50 topsoil-and-compost blend splits that into 0.59 cubic yards of screened topsoil, about 16 bags at 1 cubic foot each, and 0.59 cubic yards of compost, about 16 bags. Three blend options are shown: 50/50 topsoil plus compost, backed by Iowa State and University of Maryland extension guidance; 40/40/20 topsoil, compost, and coarse sand for drainage; and Mel’s Mix at one-third each, labeled a popular method that is not an extension standard. A note says a contained bed needs no compaction subtraction — fill, wet, then top off about 10 percent for organic settling. The calculator returns yards and bags per component, not just a single total.