Concrete column calculator
Short answer
A 12" round column 8 ft tall needs about 0.23 cubic yards of concrete — roughly 12 80-lb bags (with 10% waste). Change the diameter or height in the calculator for your exact column.
Concrete by column size (8 ft tall)
| Diameter | Typical use | Cubic yards | 80-lb bags |
|---|---|---|---|
| 8" | Deck / fence post | 0.1 | 6 |
| 10" | Deck footing | 0.16 | 8 |
| 12" | Porch / pier | 0.23 | 12 |
| 16" | Heavy pier | 0.41 | 21 |
Your exact column
Open the concrete calculatorFrequently asked questions
How much concrete for a round column or footing?
A 12" round column 8 ft tall takes about 0.23 cubic yards (12 80-lb bags). Enter your diameter and height in the calculator for other sizes.
How do I calculate concrete for a sonotube?
Concrete in a round tube = π × radius² × height. Use the radius in feet (half the diameter) and the height in feet, then divide by 27 for cubic yards. The column shape does this automatically.
How many bags for a deck footing?
A typical 10–12" deck footing 3–4 ft deep takes 1–3 80-lb bags each. Multiply by the number of footings — the calculator gives the per-column count.