Concrete Column Calculator
A concrete column calculator uses π × (diameter in ÷ 24)² × height ft ÷ 27. A 16 in round column 8 ft tall takes 0.41 yd³, about $62 at $150 per yard.
How much concrete does a round column need?
A concrete column calculator finds the volume of a round column with the cylinder formula: cubic feet = π × (diameter in inches ÷ 24)² × height in feet, then cubic yards = cubic feet ÷ 27. A 16 in diameter column that stands 8 ft tall holds 11.17 cubic feet, which is 0.41 cubic yards. At $150 per yard that is about $62 of concrete per column, before waste.
Enter height in feet and diameter in inches, as they appear on most drawings. Tick the waste box to add 10%, then multiply the result by the number of identical columns.
The formula in plain words
- Radius in feet = diameter in inches ÷ 24. Halving gives the radius, and dividing by 12 turns inches into feet, so the two steps combine into ÷ 24.
- Area of the circle = π × radius².
- Cubic feet = area × height.
- Cubic yards = cubic feet ÷ 27.
- With waste = cubic yards × 1.10, if ticked.
- Cost = cubic yards × price per yard.
Worked examples
Porch column: 16 in diameter, 8 ft tall, $150/yd³
- Radius: 16 ÷ 24 = 0.667 ft
- Cubic feet: π × 0.667² × 8 = 11.17 ft³
- Cubic yards: 11.17 ÷ 27 = 0.41 yd³, cost $62.06
- With 10% waste: 0.46 yd³, cost $68.26
Basement support column: 12 in diameter, 10 ft tall
- Radius: 12 ÷ 24 = 0.5 ft
- Cubic feet: π × 0.5² × 10 = 7.85 ft³
- Cubic yards: 0.29 yd³, or 0.32 yd³ with waste
- Cost with waste at $150/yd³: $48.00
Six of those columns need 6 × 0.32 = 1.92 yd³, which is a sensible single ready-mix order.
Concrete per foot of column height
| Diameter | Cubic feet per ft | Cubic yards per ft | Feet of column per yd³ |
|---|---|---|---|
| 8 in | 0.349 | 0.0129 | 77.3 |
| 10 in | 0.545 | 0.0202 | 49.5 |
| 12 in | 0.785 | 0.0291 | 34.4 |
| 14 in | 1.069 | 0.0396 | 25.3 |
| 16 in | 1.396 | 0.0517 | 19.3 |
| 18 in | 1.767 | 0.0654 | 15.3 |
| 20 in | 2.182 | 0.0808 | 12.4 |
| 24 in | 3.142 | 0.1164 | 8.6 |
| 30 in | 4.909 | 0.1818 | 5.5 |
| 36 in | 7.069 | 0.2618 | 3.8 |
Multiply the middle column by your height for a quick check. Doubling the diameter quadruples the concrete, because volume grows with the square of the radius.
Concrete weight in a finished column
Normal-weight concrete is about 150 lb per cubic foot. The 16 in × 8 ft porch column above holds 11.17 ft³, so it weighs roughly 11.17 × 150 = 1,676 lb once cured. That weight sits on the footing along with everything the column carries, which is why footing size matters as much as the column itself.
How to measure
- Take the diameter and height from the structural drawings, not from a guess on site.
- Use the inside diameter of the tube or steel form.
- Measure height from the top of the footing to the underside of the beam or cap.
- Count the footing separately. Spread footings under columns are usually square pads; size them with the concrete footing calculator.
Common mistakes
- Entering diameter in feet. The field expects inches. Entering 1.33 for a 16 in column gives an answer about 145 times too small.
- Using radius instead of diameter. That gives a quarter of the real volume.
- Ordering exactly the net amount. Forms bulge slightly and some concrete stays in the chute or bucket. Tick the 10% waste box.
- Pouring in lifts that set between loads. Tall columns should be placed in one continuous pour, or with joints the engineer has detailed.
Related tools
For small post-hole and deck-pier tubes counted in bags, use the sonotube calculator. The rebar calculator estimates the steel, and the concrete weight calculator tells you what a finished column weighs. Structural columns carry life-safety loads, so have a licensed structural engineer specify diameter, reinforcement, and concrete strength.
Frequently asked questions
What do the height and diameter fields mean for a column?
Height is the full poured height in feet, from the top of the footing to the top of the column. Diameter is the inside diameter of the form in inches, which is the finished concrete diameter. For a 16 in tube form, enter 16.
How many cubic yards are in a 12 inch column?
A 12 in round column holds about 0.785 cubic feet per foot of height, or 0.0291 yd³ per foot. A 10 ft tall 12 in column is 7.85 ft³, or 0.29 yd³. With the 10% waste box ticked the calculator shows 0.32 yd³.
Is this calculator suitable for load-bearing structural columns?
It gives concrete volume only. It does not decide diameter, rebar, concrete strength, or footing size. Those depend on the load, the unsupported height, and local code, so any load-bearing column should be designed by a licensed structural engineer before you order concrete.
Should I use bags or ready-mix for a column?
An 80 lb bag yields about 0.6 ft³. A 16 in × 8 ft column is 11.17 ft³, which is about 19 bags mixed and placed in one continuous pour. Several columns, or anything over about 1 yd³, are usually easier with ready-mix, though many suppliers charge a short-load fee for small orders.
Does a concrete column need rebar?
Structural round columns are almost always reinforced with vertical bars tied with spiral or hoop ties, sized by the engineer. The calculator does not subtract the small volume steel takes up, which slightly overstates the concrete and acts as a small built-in margin.
How does a round column compare with a square pier?
A circle fills about 78.5% of the square around it. A 16 in round column 8 ft tall is 11.17 ft³, while a 16 × 16 in square pier of the same height is 14.22 ft³, about 27% more concrete.
Estimates only. Verify quantities with your supplier before purchasing.