Concrete is supplied in cubic yards, hence the quantity of square feet in a cubic yard is dependent on the pouring depth. Concrete can be poured to varying degrees of thickness.
If the slab being installed is 4 inches thick, then one cubic yard of concrete will cover 81 square feet. With a thickness of 8 inches, a cubic yard contains 41 square feet. If the thickness of the slab is 1 foot, a cubic yard will only cover 21 square feet. There are concrete spills, and the filling surface is often uneven. To ensure there is sufficient concrete for the project, acquire 10 to 15 percent additional concrete than is required.