Concrete Column Calculator
Work out the concrete needed to fill round or square columns, piers, and tube forms. Enter the diameter (or side) and height and the calculator returns volume per column and for your full count. Useful for deck piers, porch posts, and Sonotube pours.
Concrete Column Diagram
How the Formula Works
Calculate cross-sectional area
Area (ft²) = π × (Diameter ÷ 2)² Converts diameter in inches to radius in feet before squaring
Calculate volume of one column
Volume (ft³) = Area × Height (ft) Scale to all columns
Total Volume = Volume per column × Number of columns Calculate bags required
Bags = ⌈Total ft³ ÷ 0.60⌉ One 80 lb bag of concrete yields approximately 0.60 cubic feet
Frequently Asked Questions
Use the cylinder formula: Volume = π × r² × height. Convert diameter to radius (diameter ÷ 2), convert all measurements to feet, then multiply. For a 10-inch diameter, 4-foot tall sonotube: r = 10/2/12 = 0.417 ft, Volume = 3.14159 × 0.417² × 4 = 2.18 ft³. Divide by 0.60 to get bags: ⌈2.18 ÷ 0.60⌉ = 4 bags. This calculator does the math for any size.
Deck pier sizing depends on load and local frost depth. Common residential deck footings use 10-inch (250 mm) sonotubes for interior posts and 12-inch (300 mm) for corner or heavily loaded posts. Your local building code specifies minimum diameter and depth requirements — depth must extend below the frost line, which ranges from 12 inches in warm climates to 60+ inches in cold northern regions.
An 80 lb bag of concrete yields approximately 0.60 cubic feet. Common sonotube volumes: 8 in × 3 ft deep = 1.05 ft³ = 2 bags; 10 in × 4 ft deep = 2.18 ft³ = 4 bags; 12 in × 4 ft deep = 3.14 ft³ = 6 bags; 16 in × 4 ft deep = 5.59 ft³ = 10 bags. For large projects, ordering ready-mix concrete is more economical than bags.
Pier footings must extend below the local frost depth to prevent heaving. Minimum depths by region: Southern US (no frost) 12–18 inches, Mid-Atlantic 24–30 inches, Midwest 36–42 inches, Northern states and Canada 48–60+ inches. Check your local building code — many jurisdictions require engineered footings for decks and structures. The frost depth map from your local authority is the authoritative reference.
A concrete footing is a horizontal pad that distributes load over a wide area of soil. A concrete pier (or column) is a vertical cylinder that transfers load down to below the frost line. Most deck and post construction uses a combination: a round sonotube pier that sits on a flared footing bell, or a simple cylindrical tube poured full depth. This calculator covers the cylindrical pier volume — add a separate calculation for any footing bell.
Bagged concrete is practical for up to about 10–15 bags per project. Mix one bag at a time in a wheelbarrow or use a small mixer. For larger projects (20+ bags or multiple large tubes), ready-mix concrete is faster, cheaper per cubic yard, and produces more consistent results. Ready-mix is typically sold in 1-yard minimum loads — use this calculator to see if your total volume justifies an order.
An 80 lb bag of concrete costs $5–$8. A 10-inch × 4-foot sonotube needs 4 bags at $6 each = $24 in material. For 8 deck piers of the same size: 32 bags = $192–$256 in concrete alone. Add sonotube forms ($8–$20 each), rebar or post-base hardware ($10–$30 per pier), and labor. Ready-mix at $150–$200 per yard becomes cost-competitive when total volume exceeds 0.5 cubic yards.
Calculate the volume for a single column (π × r² × height) and multiply by the number of columns. Enter the count in the "Number of Columns" field above — the calculator handles the multiplication automatically and gives you the total bags and volume for the entire project in one step.