Concrete & construction
Concrete Column Calculator
Works column concrete, where the cross-section is small and the placement is awkward.
Result
Column size and reinforcement come from the structural design. Cardboard tube forms also need bracing and a level base, and a tube that floats or shifts during the pour is a far more expensive problem than a quarter yard of extra concrete.
Get a Free Business AuditHow the calculation works
Cross-sectional area times height, times the number of columns, converted to cubic yards. A circular column uses pi times the radius squared for its area. The volumes are small, which means the practical difficulties of placement and consolidation matter more than the quantity.
What moves the number
- Cross-section and height per column.
- Number of columns.
- Reinforcement and cover requirements.
- Placement access and consolidation method.
Where this one goes wrong
A tall narrow column is difficult to fill without voids, because the concrete has to flow past congested reinforcement and air has to escape, and inadequate consolidation leaves honeycombing that compromises both appearance and strength. Consolidate in lifts. Reinforcement cover is the other requirement, since bars too close to the surface corrode and spall the concrete, and the cover is specified rather than approximate.
Before you quote
- Place and consolidate in lifts rather than all at once.
- Maintain the specified reinforcement cover.
- Check the mix suits placement past congested reinforcement.
Where the rules come from
Questions
About this calculator
Why do columns get voids?
Because the concrete has to flow past congested reinforcement in a narrow space and air has to escape. Inadequate consolidation leaves honeycombing that compromises appearance and strength, which is why columns are filled and vibrated in lifts.
How do I calculate a round column?
Pi times the radius squared gives the cross-sectional area, times the height for volume, divided by twenty-seven for cubic yards. Using the diameter instead of the radius gives a figure four times too large.
Why does reinforcement cover matter?
Because bars too close to the surface corrode, and corroding steel expands and spalls the concrete off. The cover is a specified dimension rather than an approximate one, and on a column it is easily lost when the cage shifts during the pour.
The formula
volume = pi x (diameter/24)^2 x height x count
Put this calculator on your site
Free to embed. Paste this where you want it to appear. It stays up to date automatically because it loads from BDEVY.
Please keep the attribution line. It is the only thing we ask in return.
How to use this calculator
- Diameter (in) (in). Enter your own figure; the page starts at 12 in.
- Height (ft) (ft). Enter your own figure; the page starts at 8 ft.
- Number of columns. Enter your own figure; the page starts at 6.
- Waste allowance (%). Enter your own figure; the page starts at 10%.
- Concrete per cubic yard ($). Enter your own figure; the page starts at $165.
The result updates as you type, so you can try a figure, see what it does to cubic yards to order, and change it back. Nothing you enter is sent anywhere or saved.
A worked example
These are the figures the calculator opens with. Every number in the results column below is produced by the same calculation the page runs, so you can follow it through before putting your own figures in.
What goes in
| Input | Value |
|---|---|
| Diameter (in) | 12 in |
| Height (ft) | 8 ft |
| Number of columns | 6 |
| Waste allowance | 10% |
| Concrete per cubic yard | $165 |
What comes out
| Result | Value |
|---|---|
| Cubic yards to order main result | 1.8 |
| Per column | 6.3 |
| Total volume | 37.7 |
| Estimated concrete cost | $288.75 |
| 80 lb bags if mixed by hand | 63 |
6 columns at 12 inches take 1.8 cubic yards, 6.3 cubic feet each.
How sensitive the answer is
Holding everything else steady and changing only concrete per cubic yard, this is what happens to cubic yards to order. It is worth knowing which of your inputs the answer actually hinges on, and which barely move it.
| Concrete per cubic yard ($) | Cubic yards to order |
|---|---|
| $83 | 1.8 |
| $124 | 1.8 |
| $165 example above | 1.8 |
| $248 | 1.8 |
| $330 | 1.8 |
Every other input is held at the example value while this one changes, which is not how a real job behaves. Treat it as a guide to which number matters most, not as five separate quotes.
What each figure means
- Diameter (in) (in)
- Measured in in, between 0 and 120, starting at 12 in.
- Height (ft) (ft)
- Measured in ft, starting at 8 ft.
- Number of columns
- A number, between 0 and 999, starting at 6.
- Waste allowance (%)
- A percentage, between 0 and 40, starting at 10%.
- Concrete per cubic yard ($)
- A money amount, starting at $165.
What the results tell you
| Result | What it is |
|---|---|
| Cubic yards to order | The headline result. A decimal figure. |
| Per column | A decimal figure. |
| Total volume | A decimal figure. |
| Estimated concrete cost | A money figure. |
| 80 lb bags if mixed by hand | A number. |
Order slightly more than this
Volume calculations assume a level, properly prepared base and exact dimensions. Sub-base variation, over-excavation and spillage all consume concrete, which is why most contractors add a margin. Running short mid-pour is far more expensive than a small overage.
Keep going
Related calculators
Estimating is the easy part
The jobs you never hear about cost more than the ones you mis-measure. BDEVY builds the marketing, systems and automation that bring them in.