Concrete Column Calculator
Enter the diameter, the height and the number of columns. For square or rectangular columns, switch to the Footing shape and enter the sides.
Last updated November 13, 2026
How to calculate concrete for a column
- Round column: 3.1416 × radius² × height.
- Square or rectangular column: side × side × height.
Example: four round columns, 12 inches across and 8 ft tall. One column is 3.1416 × 0.5 × 0.5 × 8 = 6.28 cubic feet. Four are 25.1 cubic feet, or 0.93 cubic yards.
Concrete per round column
| Diameter | Cubic feet per foot | Cubic feet at 8 ft tall | 80 lb bags at 8 ft |
|---|---|---|---|
| 8 in | 0.35 | 2.8 | 5 |
| 10 in | 0.55 | 4.4 | 8 |
| 12 in | 0.79 | 6.3 | 11 |
| 16 in | 1.40 | 11.2 | 19 |
| 18 in | 1.77 | 14.1 | 24 |
| 24 in | 3.14 | 25.1 | 42 |
Square columns
| Column size | Cubic feet per foot | Cubic feet at 8 ft tall |
|---|---|---|
| 8 in × 8 in | 0.44 | 3.6 |
| 10 in × 10 in | 0.69 | 5.6 |
| 12 in × 12 in | 1.00 | 8.0 |
| 16 in × 16 in | 1.78 | 14.2 |
| 18 in × 18 in | 2.25 | 18.0 |
| 24 in × 24 in | 4.00 | 32.0 |
A square column holds about 27% more concrete than a round column of the same width.
Before you pour
- Column forms are tall, so the pressure at the bottom is high. Brace them well.
- Structural columns need reinforcement and a design. This calculator gives the quantity only.
- For columns formed with cardboard tubes, see the sonotube concrete calculator.
Frequently asked questions
How do I calculate concrete for a round column?
Multiply 3.1416 × radius² × height, all in feet. A 12 inch column 8 ft tall is 3.1416 × 0.5 × 0.5 × 8 = 6.28 cubic feet.
How do I calculate concrete for a square column?
Multiply side × side × height in feet. A 12 inch square column 8 ft tall is 1 × 1 × 8 = 8 cubic feet. In the calculator, use the Footing shape for square or rectangular columns.
How many bags of concrete for a 12 inch column?
A 12 inch round column holds 0.79 cubic feet per foot of height. At 8 ft tall it needs 6.28 cubic feet, which is 11 bags of 80 lb mix.