CalcCoverageHow much mulch do I need?
Mulch is a volume problem: area × depth. The depth is the number people get wrong — a bag that “covers 12 sq ft” only does so at 2 inches deep, and most beds want 3 inches for real weed suppression.
Cubic yards = area (sq ft) × depth (in) ÷ 324
Example: a 20 × 4 ft bed at 3 inches deep is 80 × 3 ÷ 324 = 0.74 cubic yards — or about 14 bags of 2 cu ft with a 10% allowance.
How deep should mulch be?
| Situation | Depth |
|---|---|
| Topping up last year's mulch | 1 in (2.5 cm) |
| Standard flower and shrub beds | 3 in (7–8 cm) |
| New beds, heavy weed pressure | 4 in (10 cm) |
| Around trees (keep off the trunk) | 3–4 in (7–10 cm) |
Bags or bulk?
One cubic yard is 27 cubic feet — about 13–14 standard 2 cu ft bags. Under a yard, bags are convenient and clean. Above a yard, bulk delivery is usually far cheaper per volume and saves a dozen trips. One more honesty note: bagged mulch settles and compacts, so the 10% allowance here is doing real work.