A concrete slab is the most common pour, and the math is the same every time: length times width times thickness, then convert to cubic yards. This calculator handles the conversion so you order the right amount.
Standard slabs are 4 inches thick, while driveways and garage floors often go 4 to 6 inches. Measure the form at its deepest point and add about 10 percent for subgrade variation and spillage.
Most residential slabs are 4 inches thick. Driveways and garage floors are often 4 to 6 inches, and footings or heavy-load areas may need 8 inches or more.
Order about 10 percent more than your calculated yardage to cover uneven ground, form irregularities and spillage.