Use inside form diameter
A form tube label may not match the exact inside diameter. When precision matters, measure the actual inside opening and depth before calculating.
concrete
Concrete Column Calculator
Calculate concrete volume for round columns and piers.
Concrete Column CalculatorDiameter, depth or height, and quantity are required before the estimate appears.
Example12 in diameter x 4 ft deep = 0.12 yd³
Use the inside form diameter and include below-grade depth for piers.
Last reviewed: May 12, 2026 by the BuilderCalc editorial team.
SSR formula reference
Concrete Column Calculator formulas
These formulas are rendered in the server HTML so crawlers, LLMs, and users can read the method without running JavaScript. The interactive calculator can change the inputs, but the estimating math below is visible in the raw page source.
Volume (cubic feet) = Length x width x thickness (in inches / 12).
Volume (cubic yards) = Cubic feet / 27.
Bags (80-lb) = Cubic feet / 0.60, rounded up.
80-lb bag yields about 0.60 ft3, or 0.022 yd3.
| Result | Formula |
|---|---|
| Radius | Diameter / 2 |
| Cylinder volume | 3.1416 x radius x radius x depth |
| Cubic yards | Cubic feet / 27 |
| Bags | Cubic feet / bag yield, rounded up |
Standard PSI by application
| Application | Recommended PSI |
|---|---|
| Patio or walkway | 3,000 PSI |
| Garage floor, residential | 3,500 PSI |
| Driveway, cars | 3,500 to 4,000 PSI |
| Driveway, trucks or RVs | 4,000 to 4,500 PSI |
| Foundations and footings | 3,000 to 4,000 PSI, per plan and code |
Bag yield reference
| Bag size | Common yield |
|---|---|
| 80-lb bag | About 0.60 ft3, or 0.022 yd3 |
| 60-lb bag | About 0.45 ft3, or 0.017 yd3 |
| 50-lb bag | About 0.375 ft3, or 0.0138 yd3 |
| 40-lb bag | About 0.30 ft3, or 0.011 yd3 |
Column planning
Concrete Column Calculator planning notes
Round columns and piers are small in plan view but can add up quickly when you multiply by quantity. Measure the inside diameter of the form tube, not the outside label.
Group matching piers
Use the quantity field for identical piers. For mixed diameters or depths, calculate each group separately and add the totals.
How to use it
Keep the estimate tied to field measurements
Measure inside diameter
Use the inside diameter of the form tube, not the outside label or nominal size.
Measure depth or height
Include below-grade depth for piers and the full pour height for above-grade columns.
Enter quantity
Use quantity for identical columns. Calculate mixed sizes separately and add the totals.
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FAQ
Concrete estimating questions
How much concrete do I need for a Sonotube?
A 12 inch diameter by 4 ft deep form tube needs about 0.12 cubic yards, or about six 80 lb bags before waste. Use the calculator for other diameters and depths.
What size Sonotube should I use for a deck post?
Many residential deck posts use 10 inch or 12 inch form tubes. Larger structures, poor soil, or higher loads may require 16 inch or larger piers.
How deep should a footing column be?
In frost-prone climates, pier bottoms usually need to extend below local frost depth, often 36-48 inches. Check your local frost depth and building department guidance.
Do I need rebar in a concrete pier?
Many residential piers use two to four vertical #4 bars with horizontal ties, but reinforcement requirements depend on load, soil, and local code.
How do I calculate multiple columns?
Enter the diameter, depth, and quantity for identical columns. For mixed sizes, calculate each size separately and add the cubic-yard totals.