Concrete column calculator
Enter the column’s cross-section, height and how many there are to get the concrete in cubic yards and bags.
Enter your measurements
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)
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
- Total to buy counts this as bags. Switch “How will you buy it?” to ready-mix truck if you are ordering a delivery.
Quick answers for common sizes
| Example | Answer |
|---|---|
| How much concrete for a 12×12 column | 1 cu ft per foot: 8.4 cu ft with 5% extra for 8 ft (14 bags of 80 lb) |
Your column at other heights
| Height | Concrete to order | Or bags of mix (incl. extra) | Concrete per column |
|---|---|---|---|
| 3 ft | 0.12 cu yd | 6 bags | 3.15 cu ft |
| 4 ft | 0.16 cu yd | 7 bags | 4.2 cu ft |
| 6 ft | 0.23 cu yd | 11 bags | 6.3 cu ft |
| 8 ft | 0.31 cu yd | 14 bags | 8.4 cu ft |
| 10 ft | 0.39 cu yd | 18 bags | 10.5 cu ft |
| 12 ft | 0.47 cu yd | 21 bags | 12.6 cu ft |
A column is a prism: cross-section area × height. For a square column that is width × depth × height; for a round one, 3.1416 × radius² × height. Working in inches and feet, divide by 144 to get cubic feet.
square column (cu ft) = width (in) × depth (in) × height (ft) ÷ 144 round column (cu ft) = 3.1416 × (diameter (in) ÷ 2)² × height (ft) ÷ 144 cubic yards = cubic feet ÷ 27
| Section | Cu ft per foot of height | 80 lb bags per foot |
|---|---|---|
| 8 × 8 in | 0.44 | 0.74 |
| 10 × 10 in | 0.69 | 1.16 |
| 12 × 12 in | 1.0 | 1.67 |
| 16 × 16 in | 1.78 | 2.96 |
| 12 in round | 0.785 | 1.31 |
| 16 in round | 1.40 | 2.33 |
For round columns poured in fiber tube forms, the Sonotube calculator works per tube and the Sonotube sizes chart lists Sonoco’s diameters. A worked example for a square column is on how much concrete for a 12×12 column.
Structural columns
Columns that hold up a roof, beam or upper floor are engineered: size, reinforcement, ties and the footing under them come from your plans. The calculator only works out the concrete. Decorative columns and mailbox or gate pillars are another matter — many are hollow block or brick shells filled with concrete, which the block fill calculator covers.
Tips
- Brace forms in two directions and check them for plumb on two faces before and during the pour.
- Fill in lifts and consolidate each one — rod it or tap the form — so there are no honeycomb voids at the bottom.
- Square forms built from plywood bulge at mid-height if they aren’t clamped; add yokes every foot or two on tall forms.
What you’ll need
- Cardboard concrete tube formBudget price
Round fiber tubes form piers, columns and footings above or below grade. Sold in common diameters; cut to length with a handsaw.
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.
See options on Amazon (opens in a new tab) - 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)
As an Amazon Associate we earn from qualifying purchases. Links to products are affiliate links — they cost you nothing extra and help keep these calculators free.
Frequently asked questions
How do I calculate concrete for a round column?
3.1416 × radius² × height. A 12 in round column is 0.785 cu ft per foot, so 8 ft is 6.3 cu ft, about 11 bags of 80 lb before waste.
How much concrete is in a 12×12 column per foot?
Exactly 1 cu ft per foot of height — 12 × 12 in is one square foot. Twenty-seven feet of it is a cubic yard.
Should I use bags or ready-mix for columns?
For one or two short columns, bags are fine. For several tall columns, ready-mix with a pump is usually easier, since each column should be filled without long breaks.
Related guides
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.