Mulch is used to suppress weed growth, conserve moisture around plants and prevent soil nutrients from evaporating or running off. Mulch can be obtained from a garden store or nursery, or made from your own plant debris. The cubic yard, or simply "yard," is the common unit of measurement for mulch in the U.S. Make sure you are getting the right amount of mulch to sufficiently cover your yard by estimating your mulch needed by yard.
Measure the size of the area that you wish to cover with mulch. Convert the measurements to feet. Use a paper and a pen to jot down your measurements.
Use basic geometry to calculate the total area. For rectangular spaces, multiply the width by the length of the area. For circular areas, measure the distance from the circle's middle to its edge (the radius). Square the result, then multiply by pi (3.14) for the area's total square feet. For a rectangle-shaped area, multiply its width by its height.
Multiply the result from Step 1 by the desired depth of the mulch bed, in inches.
Divide the final number by 324, the number of square feet that a single cubic yard of mulch will cover if spread 1-inch thick. The result is the number of cubic yards you need for sufficient mulch coverage in your garden or landscape.
Use an online mulch calculator (see Resources) as an alternative to doing the calculations in your head. Enter in your garden's size and mulch needs to immediately view your cubic yard needs.
Work backwards if you already have mulch and want to know how much it will cover. Every cubic yard of mulch will add one inch of mulch over an entire 324-square-foot plot. Multiply your current cubic yardage of mulch by 324 to estimate its total coverage potential.