Ordering bulk material like dirt, topsoil, or compost requires an accurate understanding of volume. These materials are generally sold by a standardized measure of volume, not by weight. Calculating the required amount precisely helps prevent the expense of over-ordering or the delays caused by having too little material. Since the price of a cubic yard often includes a delivery fee, getting the calculation right the first time is financially beneficial. This process involves defining the unit of measure and ending with a final adjustment for real-world factors.
Understanding the Cubic Yard
The standard unit of measurement for bulk landscaping materials is the cubic yard, frequently shortened to just “yard” by suppliers. A cubic yard represents a specific volume of space: a cube measuring 3 feet in length, 3 feet in width, and 3 feet in height.
One cubic yard contains a total of 27 cubic feet (3 feet x 3 feet x 3 feet). Visualizing this volume can be helpful; a cubic yard is roughly the size of a standard washing machine or a large kitchen stove. Knowing this fixed volume is the first step before calculating how many units are needed for your project area.
Measuring Your Project Dimensions
Accurately determining the volume of dirt needed begins with precise measurements of the area you intend to fill. Measure the length, width, and depth of the target area using a tape measure. It is necessary to use a single, consistent unit of measure for all three dimensions, with feet being the most practical unit for the upcoming calculation.
Measure the length and width of the area in feet, rounding to the nearest foot or half-foot. The depth, or how thick you want the layer of dirt to be, is often measured in inches. To maintain consistency for the formula, convert this depth measurement into a decimal form of feet by dividing the number of inches by 12. For example, a depth of 6 inches is converted to 0.5 feet (6 ÷ 12).
The Essential Calculation Formula
Once all dimensions are converted to feet, the calculation to find the volume in cubic yards can be performed. The formula for calculating the cubic feet of a rectangular space is: Length × Width × Depth. This result represents the total cubic feet of material required for your project.
To convert this cubic foot total into the final cubic yard measurement, divide the result by 27. For example, if you have a garden bed that is 10 feet long, 4 feet wide, and requires a depth of 0.5 feet (6 inches), the calculation is (10 × 4 × 0.5) = 20 cubic feet. Dividing 20 cubic feet by 27 yields approximately 0.74 cubic yards of dirt. This two-step process is the most accurate method for ordering.
Practical Adjustments for Ordering
The calculated cubic yard number must be adjusted for real-world conditions before ordering. Materials like dirt and topsoil settle after placement, a process known as compaction. To account for this natural settling, add a small “compaction factor” to your total volume.
Adding between 5% and 10% to the calculated cubic yardage is standard practice to ensure sufficient material after settling occurs. If the project area is not a perfect rectangle, break the area into multiple smaller rectangles, calculate the volume for each, and then add them together. For areas with an uneven surface or slope, take several depth measurements and use the average depth for the calculation. Round your final, adjusted number up to the nearest convenient ordering amount, as most suppliers sell in full or half-yard increments.