Mulch Calculator
How much mulch you need in cubic yards, and how many 2 or 3 cubic foot bags, for any bed size and depth.
How this is calculated
Volume is length times width times depth. With feet and inches, the depth is divided by 12 to get feet, and cubic feet are divided by 27 to get cubic yards, the unit bulk mulch is sold in. With meters and centimeters, the depth is divided by 100.
Bagged mulch is sold by the volume printed on the bag, most often 2 or 3 cubic feet in the US. The number of bags is the volume divided by the bag size, rounded up, since a part bag still has to be bought. A cubic yard is 13.5 two-cubic-foot bags or 9 three-cubic-foot bags.
A layer of about 2 to 3 inches is the usual advice for garden beds; more can keep water and air from the soil. Keep mulch a few inches away from tree trunks and plant stems.
Limits
A rectangular bed of even depth. For a round bed, use the diameter for both length and width and multiply the result by 0.785 (pi divided by 4). Bags can settle in storage, so a bag may hold slightly less than its label.