Concrete Calculator

How to Calculate Concrete

Concrete volume is just length × width × thickness, with every measurement in the same unit. Because thickness is usually given in inches, divide it by 12 to convert to feet before multiplying. That gives you cubic feet; divide by 27 to get the cubic yards that ready-mix trucks are billed in. For round columns and Sonotube forms, the volume is π × radius² × height instead.

Bagged concrete is sold by weight, and the yield is roughly 0.30 ft³ per 40 lb bag, 0.45 ft³ per 60 lb bag, and 0.60 ft³ per 80 lb bag. Always order a little extra — about 10% — to account for spillage, uneven subgrade, and over-excavation. This calculator adds your chosen waste factor automatically and shows yards, bags, and ready-mix cost at once.