Topsoil is the uppermost layer of the earth’s surface, distinguished by its high concentration of organic matter, microorganisms, and essential nutrients that support plant life. This layer is the foundation for healthy lawns and gardens, making its proper application crucial for any landscaping project. Calculating the exact quantity prevents two costly errors: ordering too little and delaying the project, or ordering too much and dealing with expensive waste. The calculation involves converting the three-dimensional space of your project area into a volume measured in cubic yards.
Preparing for the Calculation: Area and Depth
The first step in calculating your topsoil requirement is to accurately define the area and the desired depth of the material. All measurements must be taken in feet, even if the final depth is planned in inches. You will need to measure the length and width of the space to determine the area in square feet.
For a rectangular or square area, simply multiply the length by the width to get the square footage. If the area is irregularly shaped, mentally divide it into several smaller, measurable squares or rectangles, calculate the area of each section, and then add them together for the total square footage.
The required depth depends entirely on the project’s scope, as different plants need varying amounts of space for root development. For overseeding an existing lawn, a thin layer of 2 to 3 inches is generally sufficient to protect the seeds. A new lawn installation typically requires a topsoil layer of 4 to 6 inches to establish a dense root system.
For flower beds and shrubs, a depth of 8 to 12 inches is often recommended to support moderate root growth. When building a vegetable garden, aim for a depth of 12 to 18 inches to ensure adequate space for deep-rooted crops. To convert the depth measurement from inches into feet for the formula, divide the number of inches by 12.
The Formula: Calculating Volume in Cubic Yards
Once you have the length, width, and depth of your project area converted to feet, you can calculate the total volume in cubic feet. The formula for this is a simple multiplication of the three dimensions: Length (ft) x Width (ft) x Depth (ft) = Total Cubic Feet.
Topsoil is almost always sold and delivered in bulk measured in cubic yards, so the next step is to convert the cubic footage. A single cubic yard is equivalent to 27 cubic feet. To perform the conversion, divide your Total Cubic Feet by 27.
For example, consider an area that is 10 feet long by 10 feet wide, with a required depth of 6 inches (0.5 feet). Multiplying these figures gives 10 ft x 10 ft x 0.5 ft, resulting in 50 cubic feet. Dividing 50 cubic feet by 27 yields approximately 1.85 cubic yards.
Finalizing the Order: Accounting for Compaction and Logistics
The calculated cubic yardage is a theoretical volume that does not account for the real-world properties of soil, requiring a final adjustment before placing the order. Soil, especially when freshly delivered in a loose state, will settle and compact over time due to watering, gravity, and foot traffic. This settling means the final depth will be less than the initial application depth if you order the exact calculated amount.
To compensate for this natural settling, it is standard practice to increase your calculated volume by 10 to 20 percent. For instance, if your initial calculation was 1.85 cubic yards, increasing that by 15% results in an adjusted order of approximately 2.13 cubic yards. It is always prudent to round this final number up to the nearest whole or half-yard increment, ensuring you have enough material to complete the project without a costly second delivery.
Consider the logistics of the delivery itself, as topsoil is typically delivered in large dump trucks. Ensure the delivery location has clear access and is a safe, appropriate dumping area, as the soil will be deposited in a large pile. Finally, be aware that topsoil is sold in bulk by the cubic yard, while smaller amounts may be available in bags measured in cubic feet, which is significantly more expensive per unit volume.