Concrete & Masonry
Updated Jul 6, 2026

Concrete Column Calculator

Calculate concrete volume, bags, rebar, and ties for round, square, and rectangular columns, piers, and sonotubes.

How to Calculate a Concrete Column

Concrete columns are cylindrical, square, or rectangular vertical elements that carry building loads down to the footings. Common residential examples include deck post footings in sonotubes, basement columns, and decorative porch columns.

Round Column Formula

Volume=π×(Diameter2)2×Height

Rectangular Column Formula

Volume=Side A×Side B×Height
Sonotube Sizing
Common sonotube diameters for residential use are 8, 10, 12, and 16 inches. A 10 in sonotube 4 ft tall holds about 2.2 cu ft (5 bags of 60lb mix). A 12 in tube 4 ft tall holds 3.1 cu ft (7 bags).

Sonotube Volume Reference (4 ft Height)

8 in
1.4 cu ft
3 of 80 lb
10 in
2.2 cu ft
5 of 60 lb
12 in
3.1 cu ft
7 of 80 lb
16 in
5.6 cu ft
12 of 80 lb

Column Reinforcement

Per ACI 318, structural columns need a minimum of 4 vertical bars for rectangular shapes and 6 for round columns, with vertical steel between 1 and 8 percent of the gross column area. Horizontal ties or hoops are placed every 12 to 16 inches to prevent buckling of the vertical bars.

Frost Line Depth
Deck piers and column footings must extend below the frost line to prevent heaving. Depths vary by region - check local codes. Typical minimums: 0 in (Florida), 32 in (Mid-Atlantic), 42 in (Canada), 60 to 80 cm (Europe).

Concrete Cover for Rebar

Maintain 3 inches (75 mm) of clear concrete cover over rebar for columns cast against earth, 2 inches (50 mm) when exposed to weather, and 1.5 inches (38 mm) for interior columns. Cover protects steel from corrosion and provides fire resistance.

Frequently Asked Questions