Concrete Column Calculator
Get the concrete needed for round columns, piers and sonotubes.
What you'll need to order
- ready-mix concrete
- sonotube forms
- rebar cage
- post base anchors
Prices vary by region and haul distance. Get quotes from at least two local suppliers.
How this calculator works
volume = π × (diameter ÷ 24)² × height × quantity
Dividing the diameter by 24 converts it to a radius in feet in one step. Sonotubes bulge slightly under the weight of wet concrete, so the real volume runs a few percent above the nominal figure.
Switch the site to metric — the control is in the footer — and your inputs, your results and the tables below follow. The formula, the constants, the guidance text and the sources stay in US units on purpose: that is how the standards they come from are written, and restating them would detach each figure from the document you are meant to be able to check it against.
Where these numbers come from
- NIST Special Publication 811 2008 — the cubic yard as 27 cubic feet, and the geometry of a right circular cylinder
Check the edition. Codes are amended every few years, and the one your inspector works from may not be the one named above.
Worked example
With diameter 12 in, height 10 ft, number of columns 1 , this calculator returns 0.32 cu yd.
Waste allowance
The headline figure includes a 10% allowance for waste and over-ordering. The exact requirement is shown alongside it.
Concrete for common sonotube pours
Every row here opens the calculator already filled in. Copy that link and the numbers travel with it.
| Job | Size | Concrete to order |
|---|---|---|
| Deck pier | 12 in × 4 ft × 6 | 0.77 cu yd |
| Porch column footing | 16 in × 4 ft × 4 | 0.91 cu yd |
| Pole barn pier | 18 in × 5 ft × 12 | 4.32 cu yd |
| Single tall column | 24 in × 10 ft × 1 | 1.28 cu yd |
| Mailbox or sign post | 10 in × 3 ft × 1 | 0.07 cu yd |
Sonotubes bulge under the weight of wet concrete, so the real pour runs a few percent above nominal.
Frequently asked questions
How much concrete does a 12 inch sonotube hold?
About 0.785 cubic feet per foot of height, so a 10 ft column takes 7.85 cubic feet — roughly 0.29 cubic yards, or 13 bags of 80 lb mix.
What size sonotube do I need for a deck post?
Ten or 12 inch diameter suits most residential deck footings. Size it from the tributary load and soil bearing capacity — larger decks and poor soil need 16 or 18 inch.
Do concrete columns need rebar?
Structural columns do — typically four vertical bars with ties, kept 3 inches clear of the form. Simple deck piers under 4 ft often need only a single centred bar, though local code decides.
How deep should a column footing go?
Below the frost line, and bearing on undisturbed soil or a widened base. A column that stops above frost depth will heave every winter regardless of how well it is reinforced.