Formula
The volume is rounded up to the next bag:
bags = ceil(length × width × depth / 12)
Mulch is reported in cubic yards. This page reports bags of one cubic foot each.
Assumptions
- One bag holds one cubic foot.
- The bed is a rectangle.
- Depth is inches.
Worked example
An 8 by 4 foot bed at 6 inches needs 16 bags.
Input definitions
- One-cubic-foot bag
- A volume bag. A 40-pound bag often holds less than a cubic foot and is not this count.
Limitations
Settling and a bag that holds 0.75 cubic feet will change how many you need. Read the volume on the bag.
Questions
Why 16 bags?
Eight times four times a half foot is 16 cubic feet, and each bag is one of them.
What about a 40-pound bag?
Weigh the volume printed on it. This page only counts bags that hold one cubic foot.