Measure the length, width, and thickness of the area in feet
Multiply length × width × thickness to get cubic feet
Divide cubic feet by 27 to get cubic yards
Use the formula: cubic yards = (length × width × thickness) ÷ 27
Convert thickness to feet if measured in inches by dividing inches by 12
Add extra for waste, spillage, and uneven ground if needed
Round up to the next practical yardage amount when ordering concrete