Concrete Column Calculator
Round tube forms or rectangular piers: enter the dimensions from your plans and the column count, and get exact cylinder or prism volumes with bag counts from manufacturer yield data. Volume only — what size a column must be is a structural question this tool deliberately does not answer.
Column shape and dimensions (from your plans)
Example: four 10 in × 8 ft round forms at 10% waste → 17.45 cu ft, 32 bags of 80 lb mix.
Structural boundary: column diameter, height, reinforcement, and footings are engineered, code-governed decisions. Use the dimensions from your approved plans; this tool only totals the concrete they hold.
Cylinders and prisms, exactly
The worked example: one 10 in form has a radius of 5 in = 5⁄12 ft, so 8 ft of it holds π × (5⁄12)² × 8 = 4.36 cu ft. Four forms total 17.45 cu ft = 0.65 cu yd; with the 10% pour allowance that is 19.2 cu ft to mix, or 32 bags of 80 lb mix at the manufacturer's 0.60 cu ft yield. Computed at build time by the same engine wired to the form.
What is sourced, what is yours
Bag yields are the QUIKRETE No. 1101 data-sheet figures (imperial) and the Canadian manufacturer's stated metric yields, locked by automated tests; π comes from mathematics. The dimensions, count, waste margin, and price are entirely yours — and so is the design: the tool will happily compute a structurally absurd column if your plans are wrong, which is why the plans, not the calculator, are the authority.
Above and below the column
The pad the pier bears on is the concrete footing calculator's job; fence and deck posts set directly in holes belong to the post hole calculator. For slabs there is the concrete slab calculator, and the concrete bag calculator compares every bag size for any volume you bring it.
Frequently asked questions
How is a round column volume computed?
Classic cylinder geometry: π × radius² × height, with the diameter converted from inches to feet first. A 10 inch form is a 5/12 ft radius, so 8 ft of it holds π × (5/12)² × 8 ≈ 4.36 cubic feet. Rectangular piers are width × depth × height. Nothing is rounded until the final ceil to whole bags.
Does this tool size my columns or footings?
No. Column diameter, height, reinforcement, and the footing underneath are structural design questions governed by code and site loads — they come from your plans, engineer, or building department. This tool converts dimensions you already have into concrete quantity, nothing else.
What about the flared footing at the base of a pier?
Compute it separately and add: a rectangular pad is the concrete footing calculator’s territory. If you use a proprietary flared form, the manufacturer publishes its volume — add it as its own quantity rather than approximating.
How many bags does a typical deck pier take?
It depends entirely on your dimensions, which is why they are inputs. As a sense check from the yield data: one 8 in × 4 ft tube holds about 1.4 cu ft, roughly two and a half 80 lb bags — the exact figure, with your waste margin and whole-bag rounding, is what the tool reports.
Why do the bag counts use Quikrete yields?
Because they are the manufacturer-published figures we can cite and test: 0.30–0.60 cu ft per bag for the 40–80 lb sizes (No. 1101 data sheet) and 0.43/0.52 cu ft for the Canadian 25/30 kg bags. If you buy another brand, its bag states its own yield — the counts scale accordingly.
Dimensions never leave your browser. Sources and the estimating pipeline are documented on the methodology page.