How the raised bed soil math works
Volume is length × width × depth, all in feet. An 8 × 4 × 1 ft bed is 8 × 4 × 1 = 32 cubic feet. There are 27 cubic feet in a cubic yard, so 32 ÷ 27 = 1.19 cubic yards. Bags are cubic feet ÷ bag size, rounded up: 32 ÷ 2 = 16 bags exactly.
If your depth is in inches, divide it by 12 first to get feet — a 12-inch-deep bed is 1 ft, and a 6-inch-deep bed is 0.5 ft.
Frequently asked questions
Should I fill the whole bed with bagged soil?
For deep beds, many gardeners fill the bottom with bulky organic matter and top with soil. This calculator gives the full volume — if you layer the bottom, you will need less soil than it shows.
Why do I need more soil after a few weeks?
Fresh soil settles and compacts once watered. That is normal — top the bed up rather than overfilling it on day one.
Bags or bulk delivery?
Bags suit one or two small beds. Once you pass about 1–2 cubic yards, bulk delivery is usually cheaper — use the cubic yards figure when you call a supplier.