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
Order about 10% over and spread 3 inches — mulch settles and decomposes, so a bed mulched to 2.5 inches in spring is bare by fall. Keep it a couple inches off trunks and stems; piling it against bark ("mulch volcanoes") rots the plant. Bulk beats bags past a single yard on both price and your back, but under half a yard the bags win once you factor a delivery fee.
How the mulch calculator works
The math behind the tool:
cubic yards = (area ft² × depth ft) ÷ 27
bags = cubic feet ÷ 2Material density
| Material | Density | Per cubic yard |
|---|---|---|
| Bark/wood mulch | 20 lb/ft³ (dry) | 0.27 tons |
Sources: Oregon State University Extension (soil and compost volume guidance).