The formula
Cubic feet = area (sq ft) × depth (in) ÷ 12 Cubic yards = cubic feet ÷ 27 Bags = cubic feet ÷ bag size (most bags hold 2 cu ft)
Example: a 10 × 20 ft bed at 3 inches deep needs 200 × 3 ÷ 12 = 50 cubic feet. That is 1.85 cubic yards, or 25 bags of 2 cubic feet.
Quick answers for common bed sizes
| Bed area | 2 in deep | 3 in deep |
|---|---|---|
| 50 sq ft | 0.31 yd³ · 5 bags | 0.46 yd³ · 7 bags |
| 100 sq ft | 0.62 yd³ · 9 bags | 0.93 yd³ · 13 bags |
| 200 sq ft | 1.23 yd³ · 17 bags | 1.85 yd³ · 25 bags |
| 300 sq ft | 1.85 yd³ · 25 bags | 2.78 yd³ · 38 bags |
| 500 sq ft | 3.09 yd³ · 42 bags | 4.63 yd³ · 63 bags |
| 1,000 sq ft | 6.17 yd³ · 84 bags | 9.26 yd³ · 125 bags |
How deep to spread mulch
2 to 3 inches suits most beds. Go up to 4 inches where weeds are a problem, and keep mulch a few inches away from tree trunks and plant stems. Topping up last year’s mulch usually takes only 1 to 2 inches.
Bags in a cubic yard
| Bag size | Bags per cubic yard |
|---|---|
| 1.5 cu ft | 18 |
| 2 cu ft | 13.5 |
| 3 cu ft | 9 |
Bulk mulch is usually cheaper once you need more than a yard or two. Add both prices above to compare.
Questions
How many bags of mulch are in a yard?
13.5 bags of 2 cubic feet, 18 bags of 1.5 cubic feet or 9 bags of 3 cubic feet.
How much area does a yard of mulch cover?
About 108 square feet at 3 inches deep, or 162 square feet at 2 inches.
How much mulch do I need for 100 square feet?
About 0.93 cubic yards, or 13 bags of 2 cubic feet, at 3 inches deep.
How deep should mulch be?
2 to 3 inches for most garden beds. Much deeper than 4 inches can keep water and air from reaching the roots.