A cubic yard represents a standard measure of volume used when purchasing bulk materials like soil, mulch, or gravel. Visualized, it is the amount of material that fits inside a cube measuring three feet long, three feet wide, and three feet high. Calculating this volume is important for any landscaping or gardening project to ensure you order the right amount of material. An accurate calculation prevents the expense of over-ordering and the delays caused by under-ordering.
Getting Accurate Measurements
The first step in calculating the required volume is to measure the three dimensions of the project area: length, width, and depth. Use a tape measure to determine the length and width of the space, recording these figures in feet. Measuring the depth requires deciding how thick the layer of new soil needs to be, which varies based on the project, such as a few inches for topdressing or a foot for a deep raised bed.
All three measurements—length, width, and depth—must be in feet before proceeding with the calculation. If the depth is measured in inches, that figure must be converted to a decimal of a foot by dividing the inches by 12. For instance, a depth of six inches converts to 0.5 feet (6 / 12). Maintaining this unit consistency is necessary to yield a correct volume in cubic feet.
The Cubic Yard Calculation Formula
The process for determining cubic yards involves a simple, two-step calculation. The first step is finding the volume of the space in cubic feet (CF) by multiplying the three measurements: Length (ft) x Width (ft) x Depth (ft) = Volume (CF). This method works for any square or rectangular area.
For example, a rectangular garden area measuring 12 feet long, 4 feet wide, and requiring a depth of 0.75 feet (nine inches) would have a volume of 36 cubic feet (12 x 4 x 0.75 = 36 CF). This intermediate number represents the total space the soil will occupy.
The second step converts the Cubic Feet total into the Cubic Yard (CY) measurement used for bulk ordering. Since one cubic yard contains exactly 27 cubic feet (3 x 3 x 3), you divide the cubic feet total by 27 to complete the conversion.
Continuing the example, 36 cubic feet is divided by 27 (36 CF / 27), resulting in 1.33 cubic yards. This final number is the theoretical volume of soil needed to fill the measured space.
Practical Adjustments for Soil Orders
The calculated volume provides the theoretical minimum amount of soil, but real-world conditions require adding a buffer to the final order. Soil delivered in bulk will settle and compact over time, reducing its volume once spread and watered. It is recommended to add a 5 to 10 percent buffer to the calculated cubic yard total to account for this settling and minor material waste.
Handling Non-Rectangular Areas
Handling non-rectangular areas, such as curved garden beds, requires estimating the area before calculating volume. You can approximate the shape by dividing it into smaller, manageable rectangles and calculating the volume for each section separately before adding them together. For a circular area, use the formula for the area of a circle (Pi multiplied by the radius squared) and then multiply that total by the depth in feet to find the cubic feet.
Ordering Increments
Soil suppliers often sell material in specific increments, typically in half-yard or full-yard quantities. If your calculation results in a non-standard number, like 1.33 cubic yards, you must round up to the nearest available ordering increment, which would likely be 1.5 cubic yards. This rounding ensures you have sufficient material to finish the project without needing an extra delivery.