How it works
The calculator finds the cross-section of one column, multiplies by its height and the number of columns, adds any extra, and divides by the yield of one bag.
Round: Per column = π × (Diameter ÷ 2)² × Height
Square: Per column = Side² × Height
Total concrete = Per column × Number of columns × (1 + Extra ÷ 100)
Bags = ⌈ Total concrete ÷ Yield per bag ⌉
⌈ ⌉ means rounding up to the next whole bag. The volume itself is not rounded.
Units are converted internally, so you can enter the diameter in inches and the height in feet; the result is shown in cubic yards and cubic feet (or cubic meters and liters). The default yield of 0.60 cu ft is QUIKRETE’s figure for an 80 lb bag of its Concrete Mix – change it to match your bag. This tool estimates material quantity only; sizes, depths and reinforcement come from your plans and local code.
Worked example
Inputs
- Column shape
- Round (tube form)
- Diameter or side
- 12 in
- Column height
- 8 ft
- Number of columns
- 1
- Yield per bag
- 0.6 cu ft
- Extra concrete
- 0 %
Result
- Total concrete
- 0.233 cu yd (6.28 cu ft)
- Per column
- 6.28 cu ft (0.233 cu yd)
- Bags
- 11
Common mistakes
- Entering the diameter as the radius, or the outside size of the form instead of the inside. Doubling the diameter makes the volume four times larger.
- Mixing units without checking the menus – a 12 in diameter and an 8 ft height work together only if each field shows the right unit.
- Assuming all bags of the same weight yield the same volume. Read the yield on the bag you are buying.
- Taking column size, height, footing or reinforcement from a calculator. Those come from your plans, local code or a qualified professional.
Assumptions and limits
- Each column is a straight cylinder or square prism of the same size along its full height.
- The volume is the concrete only. Reinforcing steel inside the form is not subtracted, and footings or flared bases are not included.
- Bags are rounded up to whole bags after the extra allowance. Without a yield, only the volume is shown.
- This is a material quantity only, not a structural design.
Frequently asked questions
How do I work out the volume of a round column?
Multiply π by the radius squared and by the height. For a 12 in (1 ft) form 8 ft tall that is 3.1416 × 0.5² × 8 ≈ 6.28 cu ft. Divide by 27 for cubic yards.
How many bags of concrete fill a column?
Divide the volume by the yield printed on the bag and round up. QUIKRETE’s data sheet lists about 0.60 cu ft for an 80 lb bag of its Concrete Mix, so 6.28 cu ft needs 11 bags before any extra.
What size and depth should my columns or piers be?
That depends on the load, the soil and your local code, including frost depth. This calculator doesn’t give sizes or depths – ask your building department or a qualified professional.
Can I use this for footings below a column?
Only if the footing is the same shape and size as the column. Calculate a wider footing separately, for example with the concrete slab calculator, and add the volumes.
Sources
- QUIKRETE Concrete Mix (No. 1101) Product Data Sheet — The QUIKRETE Companies. Yield per bag: 40 lb ≈ 0.30 ft³, 50 lb ≈ 0.375 ft³, 60 lb ≈ 0.45 ft³, 80 lb ≈ 0.60 ft³, 90 lb ≈ 0.675 ft³.
- NIST Handbook 44, Appendix C – General Tables of Units of Measurement — National Institute of Standards and Technology. Exact unit definitions: 1 in = 2.54 cm, 1 yd³ = 27 ft³, 1 US gal = 231 in³, 1 lb = 0.45359237 kg.
Method reviewed November 2, 2026