Mulch is a material spread over the soil surface as a protective ground cover in landscaping beds. When purchasing bulk materials, the industry standard unit of measurement is the cubic yard (three feet long, wide, and deep). Understanding the coverage rate of this volume is important for calculating the necessary quantity and ensuring the appropriate depth is applied. Applying the correct depth achieves horticultural benefits without wasting resources or harming plant health.
Coverage Area of One Cubic Yard
One cubic yard of mulch contains 27 cubic feet of material, which is the base for all coverage calculations. This fixed volume allows for a precise determination of how much area can be covered at various application depths. The coverage area diminishes proportionally as the layer of mulch becomes thicker.
Applying a one-inch layer provides the greatest coverage, spread over 324 square feet. Increasing the depth to two inches reduces the coverage area by half, covering 162 square feet. A three-inch layer covers approximately 108 square feet of surface area.
The standard depth for most landscape beds is two or three inches of material. A two-inch layer is sufficient for preventing weed seed germination by blocking sunlight. Increasing the depth to three inches enhances soil moisture retention and offers better insulation for plant roots against temperature fluctuations.
How to Determine Your Mulch Requirements
Calculating the amount of mulch needed begins with accurately measuring the area of your landscape beds. Determine the surface area by multiplying the length of the bed by its width to find the total square footage. For irregularly shaped areas, break the space down into smaller rectangles for individual measurement before summing the square footages.
Once the total square footage is established, use a mathematical formula to convert this area and your desired depth into cubic yards. Multiply the total square footage by the desired depth in inches, then divide that number by 324. The divisor, 324, represents the square feet a single cubic yard covers at a one-inch depth.
For example, if you have a 250 square foot area and wish to apply a two-inch layer, multiply 250 by 2 (500). Dividing 500 by 324 results in 1.54 cubic yards needed for the project. Since bulk materials are sold in whole or half-yard increments, round up to the nearest measure to ensure complete coverage.
Variables That Change Mulch Coverage
Standard coverage figures assume a uniform application of average-density material, but several factors alter the actual square footage achieved. The physical composition of the mulch influences its density and how it settles. Finer materials, such as shredded bark, compact more quickly than coarse wood chips, which maintain their volume better due to larger air pockets.
The type of terrain also affects the amount of material required. Uneven ground or areas with significant slopes require slightly more mulch to achieve the target depth compared to a flat surface. The material tends to spread thin on high spots and accumulate in depressions.
Over time, mulch naturally compacts due to weather, foot traffic, and decomposition, reducing its effective depth. As the material breaks down, it loses volume and settles, meaning the initial coverage depth decreases within one season. Mulch needs to be replenished periodically, often by applying a thinner, one-inch top dressing layer.