Primary material
62 bags
80 lb concrete mix
Use the calculated bag count as your buying starting point, then verify yield and pallet limits with the store.
Concrete column calculator
Concrete column calculator for round columns and piers.
Enter column diameter, height, count, and waste allowance to estimate cubic yards, bag count, and rough material cost.
12 in x 8 ft column
0.26 yd³
12 bags at 80 lb
Formula
pi r² h
Cylinder volume per column
Best for
Round forms
Columns, piers, porch supports
Quick reference
Concrete per round column or form tube
Volume and 80 lb bags for one column, including the default 10% waste.
| Diameter x height | Cubic feet | Cubic yards | 80 lb bags |
|---|---|---|---|
| 8 in x 4 ft | 1.5 ft³ | 0.06 yd³ | 3 |
| 10 in x 4 ft | 2.4 ft³ | 0.09 yd³ | 4 |
| 12 in x 4 ft | 3.5 ft³ | 0.13 yd³ | 6 |
| 12 in x 8 ft | 6.9 ft³ | 0.26 yd³ | 12 |
| 18 in x 8 ft | 15.6 ft³ | 0.58 yd³ | 26 |
| 24 in x 8 ft | 27.6 ft³ | 1.02 yd³ | 47 |
Use the inside diameter of the form tube, not the outside.
Quick column answers
Common round column layouts
Single 12 in column
12 in diameter x 8 ft high
0.26 yd³
12 bags at 80 lb with default 10% waste
4 porch columns
10 in diameter x 8 ft high
0.71 yd³
32 bags at 80 lb with default 10% waste
6 round piers
16 in diameter x 4 ft high
1.37 yd³
62 bags at 80 lb with default 10% waste
Round forms only
This calculator assumes a round cylinder. For square or rectangular columns, estimate the volume as a rectangular prism instead.
Shopping list
Ready to price and order
Use the calculated quantities as a starting cart, then compare store availability, delivery fees, pallet limits, and local ready-mix minimums before buying.
Large pours
Ready-mix quote check
For high bag counts, compare the bagged route against local ready-mix minimums, delivery, access, and unload time.
Optional base
Gravel base
Base depth is project-specific. Estimate it separately before adding bags or bulk gravel to the order.
Optional forms
Forms and stakes
Plan lumber, stakes, screws, release, and bracing around the perimeter and any step-downs or curves.
Store buttons open retailer search results for now. Confirm exact product yield, pickup, delivery, and pallet rules before ordering.
Formula shown
How the column calculation works
1. Convert diameter to radius in feet
radius ft = (diameter in / 2) / 12
2. Calculate one column
one column ft³ = pi x radius ft² x height ft
3. Multiply, add waste, and estimate bags
total ft³ = one column ft³ x count; bags = ceil(total ft³ with waste / bag yield)
Column edge cases
Bases, capitals, bell-shaped forms, embedded hardware, and voids should be estimated separately. Structural load, reinforcing steel, and anchoring are outside this quantity estimate.
Sources
- Quikrete product yields — bagged concrete mix yield references
- Sakrete bagged concrete references — common bag sizes and concrete mix guidance
- ConcreteNetwork concrete price guide — ready-mix and installed concrete cost context
Sources checked
Checked against
Bag yields checked against Quikrete and Sakrete product specs; price ranges against published concrete cost guides.
How we check our numbersLast updated: June 20, 2026
Estimate only.
This calculator is not a quote. Verify product yield, price, delivery minimums, and local conditions with your supplier or contractor before buying materials.
FAQ
Concrete column questions
Answers for round column volume, cylinder formulas, square columns, and structural limitations.
How do I calculate concrete for a round column? + -
Convert the column diameter to radius in feet, then multiply pi by radius squared by the column height. Multiply by the number of columns and add waste.
How much concrete is needed for one 12 inch round column? + -
For one 12 inch diameter column that is 8 feet tall, the calculator estimates about 0.26 cubic yards with the default 10% waste, or about 12 bags of 80 lb concrete mix. The waste percentage is editable.
Is a column calculator the same as a post-hole calculator? + -
The cylinder formula is similar, but the use case is different. Post holes are below-grade holes; columns are formed round pours above grade or in column forms.
Can I use this for square columns? + -
No. This page is for round columns. A square or rectangular column should be estimated as length times width times height, or as a wall/rectangular volume.
Is this column estimate structural design? + -
No. It estimates quantity and rough material cost only. Column size, reinforcement, anchoring, load, and formwork should be verified with a qualified professional.