Concrete Column Estimator Use these calculators to estimate the amount of concrete you''ll need for various projects. For slabs and walls use the first calculator. For circular items like piers, use the second one. Be sure to verify your results with your concrete supplier. For Slabs, Walkways, and Similar Projects: Diameter: Inches Height: For items with varying thickness use the average thickness or calculate each section separately. Inches Volume of concrete needed: Cubic Yards Cubic Feet