How the calculator works
Length (ft) × width (ft) × thickness (in) ÷ 324 = cubic yards. The result is then multiplied by 1 + your allowance percentage ÷ 100.
Example: 20 × 20 × 4 ÷ 324 = approximately 4.94 cubic yards. With a user-selected 10% allowance, the calculated quantity is approximately 5.43 cubic yards.
What this tool cannot decide
Slab thickness, reinforcement, mix, and edge details depend on the project. Confirm specifications and the final takeoff with the responsible professional and supplier. Use the concrete cost guide for the other factors behind an installed estimate.