Worked example: 3 inches deep
| Step | Math | Result |
|---|---|---|
| Area | 4 ft × 8 ft | 32 sq ft |
| Volume at 3 in | 32 × 3 ÷ 12 | 8.0 ft³ |
| Add 5% extra | 8.0 × 1.05 | 8.4 ft³ |
| Cubic yards | 8.4 ÷ 27 | 0.31 yd³ |
| 2 ft³ bags | 8.4 ÷ 2, rounded up | 5 bags |
| 3 ft³ bags | 8.4 ÷ 3, rounded up | 3 bags |
Mulch by depth
| Depth | Cubic feet | Cubic yards (+5%) | 2 ft³ bags | Bag cost | Bulk order (yd³) | Bulk delivered | Cheaper |
|---|---|---|---|---|---|---|---|
| 2 in | 5.3 | 0.21 | 3 | $12 | 1.0 | $115 | Bags |
| 3 in | 8.0 | 0.31 | 5 | $20 | 1.0 | $115 | Bags |
| 4 in | 10.7 | 0.41 | 6 | $24 | 1.0 | $115 | Bags |
At 3 inches, bags win: 5 bags cost about $20 versus $115 for a delivered 1.0 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 0.10 yd³ or 2 bags of 2 ft³. Keep mulch 2–3 inches away from trunks and stems.
Nearby sizes
Also see 4×10 bed , 5×10 bed, or the mulch by bed size chart. Use the mulch calculator for other sizes.