Topsoil houses the living edible and ornamental plants of the world. This uppermost layer of soil takes a beating from weathering, gardening and construction. If you've finally decided to renovate the front lawn or the garden beds desperately need a new soil layer, an accurate estimate helps determine the correct amount of soil to purchase. Whatever your reasons, purchasing a load of topsoil requires measurements and planning to acquire the correct amount for the landscape task.
Measure the length and width of each square or rectangular area requiring topsoil. For irregularly shaped areas, measure the widest point of the length and width. Jot down the measurements on a notepad.
Multiply the length times the width for each individual section. The resulting number reflects the total square footage of the area. Calculate separately for curved or irregularly shaped areas using the widest measurement of the area. Add the resulting figures from each area to determine the total square footage of the application area.
Determine the depth of topsoil required for your project. Vendors sell topsoil in measurements of cubic yards. Since the landscape needs the addition of soil in inch increments, determine the amount of soil required for the project in inches. One cubic yard of topsoil will cover a 324-square-foot area to a 1-inch depth.
Divide the overall square footage by 324 square feet. The resulting number equals the total number of cubic yards of topsoil required to complete the project to a 1-inch depth. For example, a 1,000-square-foot area divided by 324 square feet equals 3.086 cubic yards of topsoil to cover this area to a 1-inch depth.
Multiply the total number of cubic yards needed for a 1-inch depth application of topsoil by the total number of required inches for your project. The resulting figure provides the total number of cubic yards for the entire project. For example, if your planned 1,000-square-foot garden required 5 inches of topsoil, multiply 3.08 times 5 for a total of 15.43 total cubic yards of topsoil for the whole project.