Concrete Column Calculator
A 12-inch round concrete column 8 feet tall takes 6.28 cubic feet, or 0.23 cubic yards: 12 bags of 80-lb mix per column once you add 10% waste. It weighs about 940 lb when cured. In the calculator below, enter Diameter and Height/Depth in feet (1 ft for a 12-inch tube) and the number of columns as Quantity.
Pro Tips
- →Enter Diameter in feet in the main calculator: a 12-inch tube is 1 ft, a 16-inch tube is 1.33 ft
- →Include rebar reinforcement for structural columns
- →Use sonotubes or forms for round columns
- →Pour columns in one continuous operation
- →Vibrate concrete to remove air pockets
Includes 10% waste factor
Cost Estimate
Estimated material costs for your project
Recommendation: Bagged Concrete
For smaller projects, bagged concrete gives you more control and less waste.
18 bags × 80lb
0.38 cubic yards + delivery
Prices vary by location and time. Contact local suppliers for accurate quotes.
For general step-by-step instructions, read our complete When To Use Rebar and How To Pour Concrete.
What This Calculator Covers
This tool calculates concrete volume for vertical columns, pillars, and piers with round (cylindrical) or square cross-sections: porch columns, deck support piers, fence pillars, and decorative pillars. As a concrete column size calculator, it gives volume per column; load sizing is an engineer's job. Round volume is π × radius² × height; square volume is side × side × height. A 12-inch round column 8 feet tall takes 0.23 cubic yards per column. A 12×12-inch square column of the same height takes 0.30 cubic yards, about 27% more, because the circle sits inscribed inside the square. Round columns are formed with a cardboard tube; for brand tube sizes, use the sonotube calculator.
Half the Columns Entered Are 3 ft or Shorter
Calculations run on SlabCalc between Sep 17 and Oct 14, 2026 do not look like the 8-ft porch column in most examples. Across 52 imperial runs that changed the starting values, the median diameter was 2 ft, the median height 3 ft and the median quantity 4, with the middle half of heights between 2.4 and 8.75 ft; the median job total came to 1.58 cubic yards with waste (n=50 with a volume). Those dimensions look like short piers and footings, not porch columns.
A 3-ft pier is decided by how deep its base sits and what soil it bears on, so read the footing section before you order. A full-height column carrying a beam is decided by its steel, which is an engineer's call. Plug those medians in: four 24-inch piers 3 ft high are 37.7 cubic feet, or 1.40 cubic yards net and 70 bags of 80-lb mix with 10% waste.
Round Column Volume by Size
Volumes below are net (no waste); for other heights, scale linearly.
| Diameter | Volume per 4 ft (cu yd) | Volume per 8 ft (cu yd) | Volume per 12 ft (cu yd) | 80-lb Bags per 8-ft Column (incl. 10% waste) |
|---|---|---|---|---|
| 8 in | 0.05 | 0.10 | 0.15 | 6 |
| 10 in | 0.08 | 0.16 | 0.24 | 8 |
| 12 in | 0.12 | 0.23 | 0.35 | 12 |
| 16 in | 0.21 | 0.41 | 0.62 | 21 |
Multiply by your column count. Four 12-inch × 8-ft columns come to 0.93 cubic yards net and 47 bags with waste, because the calculator rounds bags up once for the whole job, not per column.
Square Column Volume by Size
| Cross-Section | Volume per 8 ft (cu yd) | 80-lb Bags per Column (incl. 10% waste) |
|---|---|---|
| 8 × 8 in | 0.13 | 7 |
| 10 × 10 in | 0.21 | 11 |
| 12 × 12 in | 0.30 | 15 |
| 16 × 16 in | 0.53 | 27 |
How Much a Concrete Column Weighs
Cured concrete runs about 150 lb per cubic foot, the same density the calculator uses for its weight output. One 12-inch × 8-ft column is 6.28 × 150 = 942 lb; a 16-inch column of the same height is about 1,676 lb, and the four 24-inch piers above total roughly 5,655 lb. Your footing carries that dead load before the column supports anything. How much weight a concrete pillar can hold on top depends on diameter, steel, strength, footing and soil, so that number has to come from a structural engineer.
Bags vs. Ready-Mix for Small Pours
A standard 80-lb bag of concrete mix yields about 0.6 cubic feet (0.022 cubic yards). Our calculator recommends ready-mix once the total including waste reaches 1 cubic yard, which four 12-inch × 8-ft columns (1.02 cubic yards) just pass.
| Project | Total Volume, net (cu yd) | 80-lb Bags (incl. 10% waste) | Practical Method |
|---|---|---|---|
| 2 × 12-in round, 8 ft | 0.47 | 24 | Bags |
| 4 × 12-in round, 8 ft | 0.93 | 47 | Bags or short-load |
| 6 × 12-in round, 8 ft | 1.40 | 70 | Ready-mix / short-load |
| 8 × 16-in square, 8 ft | 4.21 | 209 | Ready-mix |
Mixing 47 bags by hand is roughly a full day for two people; above 1 cubic yard, a short-load delivery can be cheaper once you price your time. The calculator prices ready-mix at $165-205 per cubic yard delivered; to see your total, price this pour.
Footing at the Base of a Column
A load-bearing column needs a footing beneath it to spread the load into the soil; a column poured directly on grade can settle or punch through. The footing is a wider pad, usually square or belled. Its depth is set locally, not nationally: the IRC (R403.1.4) puts exterior footings at least 12 inches below undisturbed ground and below the frost line your jurisdiction lists in Table R301.2, and Minnesota, for example, sets 42 in in the south and 60 in in the north. Width follows load and soil bearing capacity; IRC Table R403.1(1) gives prescriptive sizes for light-frame loads.
Soil can override the rule of thumb. The SlabCalc Soil Risk Index (USDA NRCS SSURGO data for 180 US cities, Oct 2026) measures soil swell (linear extensibility of the top 100 cm) of 8.7% around Dallas and 10.5% around Garland and Frisco, so on Dallas-Fort Worth clays pier depth and diameter are a question for a geotechnical report, not a table. A deck pier can be poured monolithically, a wide pad transitioning into the round column above; size the pad with the concrete footing calculator or the pier footing calculator and add that volume to this page's result.
Forms, Rebar, and Concrete Strength
Round columns use cardboard fiber tubes cut 6-12 inches longer than the finished height. Fresh concrete pushes on a form like a fluid: about 150 psf per foot of depth, so roughly 1,200 psf at the bottom of an 8-ft column. Brace every tube with 2×4 strongbacks and diagonal kickers, and pour at a controlled rate. The form bracing guide shows the layout.
| Element | Starting point | Purpose |
|---|---|---|
| Vertical bars | At least 4, totalling at least 1% of the column area (12-in round: 4 #5; 16-in round: at least 2.01 sq in of steel, e.g. 5 #6 (2.20 sq in) or 7 #5 (2.17 sq in)) | Carry axial and bending load |
| Ties | #3, spaced no more than 16 bar diameters (8 in for #4 verticals, 10 in for #5) or the column's least dimension | Confine verticals, resist shear |
| Clear cover | Commonly 1.5 in to form face, more where concrete is cast against soil | Protect steel from corrosion |
ACI 318 sets column steel between 1% and 8% of the gross section, so four #4 bars (0.71% in a 12-inch round) fall short.
For strength, use 3,000-4,000 PSI mix for residential columns. Exterior concrete in a freeze-thaw climate needs air entrainment more than extra PSI: for porches and steps exposed to severe weathering, IRC Table R402.2 sets 3,500 psi with 5-7% total air. See what PSI concrete do I need. Pour each column in one continuous lift to avoid a cold joint, and vibrate or rod the concrete around the cage, since voids cut capacity.
Structural Note
The sizes, rebar patterns and PSI values here are starting points, not a design. Any column carrying a porch beam, deck girder, roof or building post must be sized by a licensed structural engineer and built to local code; column failure is a life-safety issue. Use this page to order concrete, and pull the permit before you pour.
Sources
- IRC 2021 Chapter 4, Foundations (Colorado adoption, unamended, via UpCodes), accessed Oct 2026.
- Minnesota Rules, 1303.1600 Footing Depth for Frost Protection, published 2015-01-23.
- Quikrete, Concrete Mix No. 1101 data sheet, 2022.
- Dlubal, ACI 318-19 column design example, 2022, updated 2024.