By Zencalcy Editorial TeamLast reviewed About us
A column holds far less concrete than its footprint suggests, but formwork and height make it easy to underestimate. Round columns use πr²h and square columns use side²h; adding 10% covers spillage and any bell footing at the base.
Concrete bags and volume for round or square columns.
Round: V = π × r² × h Square: V = s² × h
Volume excludes any footing or bell at the base, which is calculated separately. Add 10% for spillage and form deflection. Height is the actual fill height, not the form length.
| Symbol | Meaning |
|---|---|
| r, s | Radius or side of the column. |
| h | Fill height. |
| V | Volume per column. |
π × 0.5² × 10 = 7.85 cu ft; with 10% extra that is 8.64 cu ft, so about 15 bags of 80 lb.
Continue with the Cement Calculator, Concrete Calculator, Concrete Block Fill Calculator, or the Concrete Stairs Calculator — or browse more cement & concrete and all construction calculators.
One foot of 12-inch column needs 0.785 cu ft, or about 1.5 bags of 80 lb. A 10 ft column takes about 13 bags with waste.
Results use standard construction estimating arithmetic: volumes from measured area and depth, unit weights from published material densities, and code-referenced spans or clearances where the page names a code. Quantities are rounded up to whole saleable units and include the stated waste allowance. These tools are planning aids, not structural design, and do not replace a licensed engineer, a local code check, or a contractor's site measurement.
Reference material used to build and check this calculator:
Last reviewed: September 2026. See how we build and check every tool on the about page.
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Content updated: September 2026