Measure the length, width, and thickness of the area in feet
Multiply length × width to get square feet
Multiply square feet × thickness in feet to get cubic feet
Divide cubic feet by 27 to get cubic yards
Add 5% to 10% extra for waste and spillage
For round areas, use π × radius × radius × thickness
For steps, slabs, and footings, calculate each section separately and add them together
Convert inches to feet by dividing by 12
Convert cubic feet to cubic yards by dividing by 27
Order concrete in cubic yards from the total calculated amount