Use this simple 3-step formula to calculate how much mulch you will need to cover your garden with a layer of mulch.
Let's use Joe's garden for an example.
Step 1: Calculate the area of the garden by multiplying the width (in linear feet) by the length (in linear feet).
Length X Width = Area (square feet)
Joe's garden is 40 feet long by 15 feet wide.
40 X 15 = 600
Step 2: Multiply the area of your garden by the height (depth) (in linear feet) desired - for example, 0.25 for a 3" layer of mulch.
Area X Height = Volume (cubic feet)
Joe's garden has poor drainage and is rather wet so he decides to spread a thin 2" layer of mulch.
600 X .17 = 102
Step 3: Most mulches are sold by the cubic yard. Divide the volume by 3 cubic feet (27) to find the dimensions in cubic yards.
Volume (cubic feet) / 27 = Volume (cubic yards)
Joe wants to know how many yards of mulch he needs to purchase.
102 / 27 = 3.78
Joe places an order for 4 yards of mulch.