Worked example: 3 inches deep
| Step | Math | Result |
|---|---|---|
| Area | 12 ft × 12 ft | 144 sq ft |
| Volume at 3 in | 144 × 3 ÷ 12 | 36.0 ft³ |
| Add 5% extra | 36.0 × 1.05 | 37.8 ft³ |
| Cubic yards | 37.8 ÷ 27 | 1.40 yd³ |
| 2 ft³ bags | 37.8 ÷ 2, rounded up | 19 bags |
| 3 ft³ bags | 37.8 ÷ 3, rounded up | 13 bags |
Mulch by depth
| Depth | Cubic feet | Cubic yards (+5%) | 2 ft³ bags | Bag cost | Bulk order (yd³) | Bulk delivered | Cheaper |
|---|---|---|---|---|---|---|---|
| 2 in | 24.0 | 0.93 | 13 | $52 | 1.0 | $115 | Bags |
| 3 in | 36.0 | 1.40 | 19 | $76 | 1.5 | $135 | Bags |
| 4 in | 48.0 | 1.87 | 26 | $104 | 2.0 | $155 | Bags |
At 3 inches, bags win: 19 bags cost about $76 versus $135 for a delivered 1.5 yd³ (which includes a $75 delivery fee).
Prices used: 2 ft³ bag $4, 3 ft³ bag $6; bulk mulch $40/yd³ plus $75 delivery (1 yd³ minimum). Spring sales change the crossover.
Top-ups and depth
If the bed already has mulch, a 1 inch refresh takes only 0.47 yd³ or 7 bags of 2 ft³. Keep mulch 2–3 inches away from trunks and stems.
Nearby sizes
Also see 10×20 bed , 20×20 bed , 10×10 bed, or the mulch by bed size chart. Use the mulch calculator for other sizes.