Concrete Column Calculator

A 12 in round column holds about 0.79 cubic feet per foot of height, so an 8 ft column takes about 6.3 cubic feet — roughly 11 bags of 80 lb concrete. Four of them come to about 0.93 cubic yards.

Volume = π × radius² × height. Convert the diameter to feet first: a 12 in tube has a 0.5 ft radius, so π × 0.5² = 0.785 cubic feet per foot of height. The calculator does the conversion for you.

Per foot of depth: an 8 in tube holds about 0.35 cu ft, a 10 in about 0.55, a 12 in about 0.79, and a 16 in about 1.40. Multiply by the depth and the number of tubes.

Structural columns and piers normally need vertical rebar tied with ties or spirals, sized by an engineer or local code. Short deck piers often use a single vertical bar or an anchor. Always confirm reinforcement with your local building department.