Topsoil is measured and sold according to volume. In small quantities, such as in small bags, it is measured in cubic feet, liters or cubic yards. Larger quantities that are stored and transported loosely in truck beds is most commonly measured in cubic yards. One cubic yard equals 27 cubic feet, a solid cube measuring 3 feet tall by 3 feet wide by 3 feet deep.
Use the base definition of 1 yard equals 3 feet.
Define one cubic yard as 27 cubic feet. This is determined by changing the yard measurement into feet and then multiplying the "cube" height of three feet by the width of three feet by the depth of three feet: 3 x 3 x 3 = 27 cubic feet.
Convert the smaller quantities of cubic-foot measurements to determine the coverage area of a cubic yard. For example, if you needed 10 2-cubic-foot bags of topsoil to cover beds in previous seasons, they equaled 20 cubic feet. Since one cubic yard equals 27 cubic feet, divide 20 by 27. That produces an answer of .74 , meaning you need nearly three-fourths of a cubic yard of topsoil to cover the same beds.