Concrete Column Calculator
Calculates concrete volume for above-ground round or square structural columns, vertical reinforcing rebar bars, and lateral tie hoop stirrups.
Formula
Round Vol = π × r² × H × Count; Square Vol = W² × H × Count
1. Round: Cu Ft = π × (Diameter in ÷ 24)² × Height ft × Count 2. Square: Cu Ft = (Width in ÷ 12)² × Height ft × Count 3. Total Cu Ft with Waste = Cu Ft × (1 + Waste %) 4. Cubic Yards = Total Cu Ft ÷ 27 5. Vertical Rebar = 4 vertical #4 bars per column × (Height + 2 ft overlap)
Inputs
- Column Shape
- Diameter (Round) or Width (Square) in Inches
- Column Height
- Number of Columns
Worked example
Pouring 4 architectural load-bearing porch columns using 12" cardboard form tubes.
Outcome: Each column volume is 7.07 cu ft (28.27 cu ft total for 4 columns). With 8% waste (30.54 cu ft total), you need 1.13 cubic yards (or 51 bags of 80 lb concrete). Vertical rebar: 16 ten-foot bars.
Why must vertical rebar be tied with lateral hoops/ties in columns?
Under heavy compressive loads, vertical rebar will bow outward (buckle) unless constrained by horizontal tie stirrups spaced every 8 to 12 inches along the column height.