The simple formula: (Square Feet × Depth in inches) ÷ 324 = Cubic Yards Needed. Every Ottr product page has a built-in calculator that does this math automatically based on your project area and depth. No matter what material you're buying, it follows this same formula.
The formula explained
- Square feet = the area you're covering (length × width)
- Depth (in inches) = how thick the material layer should be
- 324 = the conversion factor (12 inches per foot × 27 cubic feet per cubic yard)
- Result = cubic yards of material needed
Worked examples by common project
| Project | Area | Depth | Math | Order |
|---|---|---|---|---|
| Mulch refresh on existing beds | 500 sq ft | 3" | (500×3)÷324 = 4.6 | 5 cy |
| New lawn topsoil install | 1,000 sq ft | 4" | (1,000×4)÷324 = 12.3 | 13 cy |
| Driveway gravel top coat | 16'×40' = 640 sq ft | 4" | (640×4)÷324 = 7.9 | 8 cy |
| Paver patio bedding sand | 12'×12' = 144 sq ft | 1" | (144×1)÷324 = 0.44 | 1 cy (our minimum) |
| Raised garden bed fill | 4'×8' = 32 sq ft | 12" | (32×12)÷324 = 1.18 | 1.2 cy |
| French drain backfill | 50' × 1' wide | 18" | (50×18)÷324 = 2.78 | 3 cy |
Round up, never down
It's better to have a few extra cubic feet than to come up short and need a second delivery (which doubles delivery cost). Round to the next half-yard or full-yard above your calculation.
For irregular shapes
Break the area into rectangles and triangles, calculate each, then sum. Or measure the longest length and average width — close enough for landscape material orders.
Easiest path: use the calculator on the product page. Browse our product catalog — every page has the live calculator. Or see our weight + coverage guides for material-specific deep dives.
