Raised beds fill by volume, which is always more than the area suggests — a 4×8 bed a foot deep is about 32 cubic feet. This view takes bed length, width, and depth; top up after the first watering settles the mix.
Why order extra? The headline number is the exact material your project needs. When you actually order, add about 5–10% on top — the “with 5% waste” figure in the result is a safe starting point. That margin covers what you lose to compaction, cuts around edges and corners, and ordinary spillage during handling. It is cheaper to have a little left over than to stop mid-job and wait on a second delivery.
Field notes
Raised beds need more soil than people guess because you're filling a volume, not covering an area — a 4×8 bed a foot deep is 32 cubic feet, roughly 21 bags. Order 10% over for settling, and top up after the first heavy watering when the mix compacts. Blend in compost as you fill rather than layering it; roots don't like a hard interface between mixes.
How the raised bed soil calculator works
The math behind the tool:
cubic feet = length ft × width ft × depth ft
bags = cubic feet ÷ bag sizeMaterial density
| Material | Density | Per cubic yard |
|---|---|---|
| Garden soil | 80 lb/ft³ | 1.08 tons |
Sources: Oregon State University Extension (soil and compost volume guidance).