Mulch formula
Cubic feet = Length (ft) × Width (ft) × Depth (in) ÷ 12
Cubic yards = Cubic feet ÷ 27
Bags = Cubic feet ÷ Bag size
Cubic yards = Cubic feet ÷ 27
Bags = Cubic feet ÷ Bag size
Example: A 20 × 10 ft bed (200 sq ft) at 3 inches deep needs 50 cubic feet of mulch — 1.85 cubic yards, or 25 bags of 2 cu ft (1.42 m³, about 1,416 liters).
Coverage of one cubic yard
- 2 inches deep: 162 sq ft
- 3 inches deep: 108 sq ft
- 4 inches deep: 81 sq ft
Laying a gravel path too? Use the gravel calculator.
Frequently asked questions
How much mulch do I need?
Multiply area (sq ft) by depth (in) and divide by 12 to get cubic feet; divide by 27 for cubic yards. A 20 × 10 ft bed at 3 inches needs 50 cu ft, or 1.85 cubic yards.
How many bags of mulch are in a yard?
One cubic yard equals 27 cubic feet: 13.5 bags of 2 cu ft or 9 bags of 3 cu ft.
How deep should mulch be?
Two to three inches for most beds. Less than 2 inches does little to suppress weeds; more than 4 inches can starve roots of oxygen. Keep mulch a few inches away from stems and trunks.
Is bulk mulch cheaper than bags?
Usually, once you need more than about 2 cubic yards. Bulk mulch is sold by the cubic yard and often has a delivery fee.