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.
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.
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.