A cubic yard is a standard unit of volume used in landscaping and construction, defined as 27 cubic feet (a cube measuring three feet long, wide, and high). Since landscaping materials like mulch are sold based on the space they fill, understanding this measurement is the first step toward a successful project. This guide provides a straightforward methodology for calculating the volume of mulch needed for any garden bed, preventing the inconvenience and added expense of ordering multiple small deliveries or dealing with excess material.
Determining Essential Measurements
The calculation for mulch requires two fundamental measurements: the area of the space to be covered and the desired depth of the material. Measuring the area, expressed in square feet, is the foundation of the calculation. For simple square or rectangular planting beds, find the area by multiplying the length by the width.
For garden beds with irregular or curved shapes, divide the space into smaller, manageable sections, such as rectangles or triangles. Calculate the area of each shape individually and then add them together to obtain the total square footage. Precise measurement minimizes errors that would be compounded in the final volume calculation.
The other necessary input is the thickness of the mulch layer, referred to as the depth, measured in inches. For general landscaping, the recommendation for mulch depth is between two and four inches. A layer of two to three inches is sufficient for suppressing weeds and retaining soil moisture without suffocating plant roots. Applying mulch too thickly (more than four inches) can create problems like excess moisture, which may lead to root rot.
Calculating Cubic Yards Required
Once you have the total area in square feet and the desired depth in inches, you can calculate the volume in cubic yards using a single formula. The calculation converts the area and depth into cubic feet and then divides by 27. The most direct formula is to multiply the total square footage by the desired depth in inches, and then divide that result by the constant 324.
The constant 324 combines the two conversion steps: dividing by 12 (inches to feet) and dividing by 27 (cubic feet to cubic yards). This combined formula simplifies determining the volume needed for bulk ordering. For example, if a garden bed measures 100 square feet and you apply mulch three inches deep, the calculation is (100 x 3) / 324, resulting in approximately 0.93 cubic yards.
Real-World Adjustments and Ordering Tips
After the mathematical calculation, apply real-world adjustments to the final volume before placing an order. Suppliers suggest ordering slightly more than the calculated amount to account for common variables. Mulch naturally settles over time and may compress during delivery, meaning the actual coverage will be slightly less than the theoretical volume.
Ordering a small buffer, often rounding up to the nearest half-yard, helps ensure you do not run out of material before the job is finished. It is always better to have a small amount of leftover material than to require a second, small-volume delivery that often incurs a separate delivery fee.
If purchasing mulch by the bag instead of in bulk, a simple conversion is necessary. One cubic yard equals 27 cubic feet. Since the most common size for bagged mulch is two cubic feet, you need approximately 13.5 bags to equal one cubic yard. If your calculation shows a need for two cubic yards, purchase 27 bags of the two-cubic-foot size.
Bulk delivery is more cost-effective for larger projects and is typically sold in whole or half-yard increments. When ordering bulk material, having your calculated cubic yard volume ready allows the supplier to schedule the correct size of delivery vehicle and ensures an efficient drop-off process.