How much concrete for a 12×12 column?
A 12 × 12 inch column holds 1 cubic foot of concrete per foot of height. An 8 foot column is 8 cubic feet; with 5% extra that is 8.4 cu ft — 14 bags of 80 lb mix, or 0.31 cubic yards.
How to work it out
- 12 in × 12 in × 8 ft + 5% = 8.4 cu ft per column
- × 1 = 0.31 cu yd ÷ 0.6 cu ft per 80 lb bag = 14 bags
Twelve by twelve is the easiest column there is to estimate, because its cross-section is exactly one square foot. Every foot of height is one cubic foot of concrete.
Adjust for your project
More options: Extra
- Or bags of mix (incl. extra)
- 14 bags · 80 lb bag
- Concrete per column
- 8.4 cu ft
- Weight of the concrete (≈ 145 lb/cu ft)
- 1,160 lb (1 tons)
- Total to buy counts this as bags. Switch “How will you buy it?” to ready-mix truck if you are ordering a delivery.
12×12 column at other heights (5% extra)
| Height | Concrete per column | Or bags of mix (incl. extra) | Concrete to order |
|---|---|---|---|
| 3 ft | 3.15 cu ft | 6 bags | 0.12 cu yd |
| 4 ft | 4.2 cu ft | 7 bags | 0.16 cu yd |
| 6 ft | 6.3 cu ft | 11 bags | 0.23 cu yd |
| 8 ft | 8.4 cu ft | 14 bags | 0.31 cu yd |
| 10 ft | 10.5 cu ft | 18 bags | 0.39 cu yd |
| 12 ft | 12.6 cu ft | 21 bags | 0.47 cu yd |
From one column to a row
Eight cubic feet is 13.3 bags of 80 lb before waste, 14 with 5%. Four of them — a carport or pergola on four columns — is 33.6 cu ft with the extra, about 1.24 cubic yards or 56 bags. At that point a ready-mix delivery with a pump or wheelbarrows is worth pricing, because each column should be filled in one go.
A round column 12 in across holds 21.5% less than the square one, because a circle fills 78.5% of the square around it: 6.3 cu ft for 8 ft, or about 11 bags. The variants below compare the two.
Forms for a square column
A 12 × 12 form is four plywood sides held by clamps or wooden yokes. The concrete pushes hardest near the bottom, so space the yokes closer together there. Chamfer strips in the corners give crisp, chip-resistant edges. Size, reinforcement and the footing under a structural column come from your plans; the footing calculator adds the concrete for a pad under each one, and round tube forms are covered on how many bags of concrete for a 12 inch Sonotube.
Different size? Use the full Concrete Column Calculator.
What you’ll need
- Steel form stakesMid-range price
Round steel stakes with nail holes hold slab and curb forms in line. Easier to drive and pull than wooden ones.
See options on Amazon (opens in a new tab) - Post levelBudget price
Straps to a post or tube form and reads plumb in both directions at once, so you can set it while the concrete is still soft.
See options on Amazon (opens in a new tab) - Portable electric concrete mixerPremium price
A small drum mixer turns a long day of hand-mixing into batches of two or three 80 lb bags. Check the drum size against the bag count you need.
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Frequently asked questions
How much concrete for a 12 inch round column 8 feet tall?
6.6 cu ft with 5% extra, or 11 bags of 80 lb.
How much concrete for four 12×12 columns 8 feet tall?
1.24 cubic yards with 5% extra, or 56 bags of 80 lb.
How much concrete for a 16×16 column 10 feet tall?
18.7 cu ft with 5% extra (32 bags of 80 lb).
Sources
- Quikrete Concrete Mix (No. 1101) data sheet (opens in a new tab) — Yields: 40 lb ≈ 0.30, 50 lb ≈ 0.375, 60 lb ≈ 0.45, 80 lb ≈ 0.60, 90 lb ≈ 0.675 cu ft; unit weight ≈ 140 lb/cu ft; for pours 2 in thick or more; 6–9 pints of water per 80 lb bag; control joints every 6–8 ft; cure 5 days at 70 °F or above, 7 days at 50–70 °F; protect from freezing for 48 hours.
- Sonoco — Sonotube round concrete forms brochure (opens in a new tab) — Diameters 6 to 36 in; standard length 12 ft; concrete requirements in cubic yards by diameter and height.
- NIST Handbook 44, Appendix C — General Tables of Units of Measurement (opens in a new tab) — 1 cubic yard = 27 cubic feet; 1 cubic foot = 1,728 cubic inches.