Concrete Column Calculator
The concrete needed for round or rectangular columns and piers — per column and for the whole set, in bags or by volume.
Concrete for columns and piers.
How the concrete column calculator works
A column is a prism: cross-sectional area × height. For a round column that is πr²h, for a rectangular one w × d × h.
The useful figure is usually per-column, then multiplied. A 300 mm round column 3 m tall is 0.212 m³ — 21 twenty-litre bags, which is why anything beyond a couple of columns is worth ordering ready-mixed.
Formula: V = π r² h (round) or w d h (rectangular)
Worked examples
| Inputs | Total concrete | Note |
|---|---|---|
| Four 300 mm round columns, 3 m tall | 0.933 | 0.93 m³ with waste |
| One column only | 0.233 | 0.23 m³ — 24 bags |
| Square columns instead | 1.188 | about 27% more concrete |
FAQFrequently asked questions
How much concrete is in a 300 mm round column?
0.0707 m³ per metre of height — so a 3 m column is 0.212 m³, about 21 twenty-litre bags.
Round or square — which uses more?
Square, by about 27%, for the same nominal dimension. A 300 mm square is 0.09 m² against a 300 mm circle's 0.0707 m².
When should I switch to ready-mixed?
Past about one cubic metre. Fifty bags of hand-mixed concrete is a long day and the joins between batches are a weakness.
Why allow 10% waste?
Formwork leaks, tubes are cut long, and you do not want to run out mid-pour. A column must be poured in one go.
Does this include the reinforcement?
No. Steel displaces a negligible fraction of the volume — under 2% at normal reinforcement ratios.
Where these figures come from
- The Engineering ToolBox — material densities, coverage and unit data — bulk densities, concrete at 2,400 kg/m³, board and sheet sizes
- Cement Concrete & Aggregates Australia — concrete basics and yields — bag yields, density 2,400 kg/m³
- Australian Building Codes Board — the National Construction Code
Last checked: September 2026. Coverage rates and material sizes are typical manufacturer figures — check the product you buy.