How many yards of concrete in a 30 x 40 slab?

To calculate the number of yards of concrete needed for a 30 x 40 slab, first determine the volume in cubic feet. The volume is calculated as length × width × thickness. Assuming a standard thickness of 4 inches (1/3 feet), the volume is 30 × 40 × (1/3) = 400 cubic feet. Since there are 27 cubic feet in a cubic yard, divide 400 by 27, resulting in approximately 14.81 cubic yards of concrete needed for the slab.