When purchasing bulk landscaping materials, such as mulch, you buy it by volume, measured in cubic yards. Mulch yardage is the total three-dimensional space the material will occupy in your garden beds. Determining the precise volume needed is important for efficiency. Ordering too little will halt your project, while ordering too much leads to material waste and disposal effort. The goal is to accurately calculate the required cubic yards for complete coverage.
Measuring the Coverage Area
The first step in calculating mulch needs is to determine the total surface area of the space you plan to cover. This measurement must be taken in feet, as the final calculation relies on a consistent unit of measure for length, width, and depth. For standard rectangular or square planting beds, use a tape measure to find the length and the width of the area. Multiplying the length by the width provides the total square footage of the bed.
If you are working with an irregularly shaped area, the process requires a practical simplification. Mentally divide the complex space into smaller, manageable geometric shapes, such as rectangles, squares, or triangles. Measure the length and width for each section individually, calculating the square footage for each piece. Summing the square footage of all the smaller sections provides the approximate total square footage of the entire irregular area.
The Standard Formula and Unit Conversion
Determining mulch yardage involves a calculation that transforms the two-dimensional area into a three-dimensional volume. The standard formula requires multiplying the length, width, and depth, all measured in feet, and then converting the resulting cubic feet into cubic yards. The process is expressed as: (Length in feet × Width in feet × Depth in feet) / 27 = Cubic Yards.
A significant point of potential error is the depth measurement, which is typically measured in inches. To correctly use the formula, you must convert the desired depth from inches into feet. Since there are 12 inches in one foot, this conversion is accomplished by dividing the desired depth in inches by 12. For instance, a depth of 3 inches converts to 0.25 feet (3 ÷ 12).
Once the area’s length and width in feet have been multiplied by the converted depth in feet, the result is the total volume of mulch needed in cubic feet. The final step is to divide this cubic footage by 27. This division is necessary because a cubic yard represents a volume that is 3 feet long, 3 feet wide, and 3 feet deep, meaning one cubic yard contains exactly 27 cubic feet of material (3 × 3 × 3 = 27). This final division by the conversion factor of 27 provides the exact number of cubic yards to order.
Depth Recommendations and Ordering Adjustments
The depth of mulch applied directly impacts the final required yardage and the effectiveness of the material in the landscape. For established beds where you are refreshing the appearance, a shallower depth of 2 to 3 inches is sufficient to maintain a clean aesthetic and conserve soil moisture. For initial applications or for areas where weed suppression is a concern, a greater depth of 3 to 4 inches is recommended for most organic mulches.
Applying mulch too thickly, exceeding 4 inches, can restrict oxygen from reaching the plant roots and may cause fungi or root rot. Conversely, a layer thinner than 2 inches may not be dense enough to block sunlight and prevent weed seed germination. The optimal depth is a balance between these biological factors and the type of material, with coarser mulches sometimes requiring the upper end of the depth range.
After performing the calculation, it is good practice to slightly increase the final quantity to create a buffer. Calculated yardage represents the theoretical minimum volume required for perfect coverage. Factors like uneven ground, material settling, or minor spillage during application can cause a shortage. A common recommendation is to add an extra 5% to 10% to the calculated cubic yard total before placing the order. This adjustment helps ensure the project can be completed in a single delivery, preventing the delay and expense of ordering a small supplemental amount later.