How the mulch math works
- Area in square feet. Length × width for a bed, or π × radius² for a ring.
- Volume in cubic feet. Area × depth, with the depth in feet (inches ÷ 12).
- Bags. Divide by the bag size printed on the bag and round up.
- Cubic yards. For bulk mulch, divide cubic feet by 27.
Example: a 10 × 20 ft bed is 200 sq ft. At 3 inches deep that's 200 × 0.25 = 50 cubic feet: 25 two-cubic-foot bags, or 1.85 cubic yards of bulk mulch.
Mulch coverage chart
Two-cubic-foot bags (and cubic yards) by area and depth.
| Area | 2" deep | 3" deep | 4" deep |
|---|---|---|---|
| 50 sq ft | 5 bags (0.31 yd³) | 7 bags (0.46 yd³) | 9 bags (0.62 yd³) |
| 100 sq ft | 9 bags (0.62 yd³) | 13 bags (0.93 yd³) | 17 bags (1.23 yd³) |
| 200 sq ft | 17 bags (1.23 yd³) | 25 bags (1.85 yd³) | 34 bags (2.47 yd³) |
| 300 sq ft | 25 bags (1.85 yd³) | 38 bags (2.78 yd³) | 50 bags (3.7 yd³) |
| 500 sq ft | 42 bags (3.09 yd³) | 63 bags (4.63 yd³) | 84 bags (6.17 yd³) |
| 1000 sq ft | 84 bags (6.17 yd³) | 125 bags (9.26 yd³) | 167 bags (12.35 yd³) |
Mulching tips
- Topping up an existing bed? Measure the depth already there and enter only the difference.
- Keep mulch off tree trunks. Illinois Extension says piling it against the trunk is one of the most common causes of tree decline.
- Break up matted old mulch with a rake before adding more; you may need less than you think.
- Edging a new bed with concrete or pavers? Try the concrete calculator.