Calculating concrete measurements is a simple volumetric calculation that may require a few conversions (see Tips). Concrete is best calculated by the cubic yard or by fractions of a cubic yard. Having a calculator handy will make these calculations easier.
Find the area of the planned concrete slab by measuring the length and the width of the available space for the slab. Multiply these two measurements together (length x width).
Determine the desired thickness of the slab. A 4-inch thickness is plenty for most applications. If you plan on pouring a slab that will be used to store really heavy items, such as an RV, a 6-inch thickness would be advisable.
Multiply the area by the desired thickness [(length x width) x thickness]. It is easiest to begin with inches and convert them to cubic yards. For example: Length = 112 inches Width = 94 inches Thickness = 4 inches [(length x width) x thickness] = (112 x 94) x 4 = 10,528 x 4 = 42,112 cubic inches
Divide the number of cubic inches by 1 cubic foot to find the number of cubic feet: 42,112 / 1,728 = 24.37 cubic feet
Divide 1 cubic yard into the number of cubic feet: 24.37 / 27 = .9026 cubic yards Call your local concrete supplier and order this amount of concrete for your project.