A cubic yard of mulch equals 27 cubic feet. The number of bags needed to make up one cubic yard depends on the bag size:

• For 2 cubic feet bags (most common), you need about 13.5 bags per cubic yard.
• For 3 cubic feet bags, you need 9 bags per cubic yard.
• For 1.5 cubic feet bags, you need 18 bags per cubic yard.
• For 1 cubic foot bags, you need 27 bags per cubic yard

To figure out how much mulch you need without knowing last year's usage, measure the square footage of your garden bed (length × width) and then calculate the volume based on the desired mulch depth (usually 2-4 inches). For example, a 2-inch depth of mulch over 12 square feet corresponds roughly to one 2 cubic foot bag of mulch. You can use this formula to estimate bags needed:

Bags=Square footage×Depth in inches12×Bag size in cubic feet\text{Bags}=\frac{\text{Square footage}\times \text{Depth in inches}}{12\times \text{Bag size in cubic feet}}Bags=12×Bag size in cubic feetSquare footage×Depth in inches​

For instance, a 200 sq ft bed at 2 inches depth with 2 cu ft bags would require about 17 bags (200 ÷ 12 = 16.67, rounded up)

. In summary:

Bag Size (cu ft)| Bags per Cubic Yard (27 cu ft)| Coverage at 2-inch Depth (sq ft per bag)
---|---|---
1| 27| ~6 (approximate)
1.5| 18| ~8
2| 13.5| 12
3| 9| 18

This helps you convert between bags and yards of mulch and estimate how many bags to buy based on your garden size and desired mulch depth