Updated · Built and checked by the PlinzoTools team, formulas tested against published sources
Calculate concrete volume for round (Sonotube) or square columns and piers, including multiple identical columns.
This calculator sizes vertical concrete columns or piers -- the kind poured into a round cardboard form tube (commonly called a Sonotube) or a square wooden form -- for deck footings, fence post piers, or small structural columns. Unlike a flat pour, a round column's volume follows the geometry of a cylinder, not a rectangular prism, so it needs its own formula.
Choose round or square, enter the diameter (for round) or side length (for square) in inches and the height in feet, and set a quantity if you're pouring several identical columns at once -- a deck, for example, commonly needs 4 to 8 identical footings.
Round: Volume = π × (Diameter÷2)² × Height
Square: Volume = Side² × Height
The round formula is the standard cylinder-volume equation, using the radius (half the diameter) squared. Both formulas take the size in inches and the height in feet, converting the size to feet internally so every dimension shares the same unit.
Deck and porch footings, fence post piers poured as solid columns (rather than backfilled with dry concrete mix -- see the Fence Post Calculator for that approach), and small structural or mailbox-post columns all use this shape. For a continuous strip footing under a wall instead of individual piers, use the Concrete Footing Calculator.
Footing size and depth (especially how deep a footing must sit below grade to clear the local frost line) are structural and code decisions -- check your local building department's requirements before finalizing dimensions, since undersized or too-shallow footings can shift or heave over time.
Suppose a deck plan needs 6 round piers, each 10 in in diameter and 3.5 ft tall. The radius is 5 in, or 0.4167 ft. One column is π × 0.4167² × 3.5, which is about 1.91 cubic feet. Six columns total 11.45 cubic feet. Adding 10 percent gives about 12.6 cubic feet, or roughly 0.47 cubic yards. That is a quantity many people would mix from bags rather than order from a truck, so compare the number of bags to a delivery option.
π × (10 ÷ 24)² × 3.5 = 1.91 cu ft per column
A round column with a 12 in diameter holds about 78.5 percent of the concrete a 12 in square column of the same height would use. If you are choosing between a tube form and a box form, keep that difference in mind, but remember that the structural performance and code requirements are what should drive the shape, not just cost.
Some footings include a flared base to spread the load. The calculator treats the column as a straight cylinder or prism, so a bell shape at the bottom adds volume that you should estimate separately. The waste allowance helps cover small differences, but a large flare needs its own calculation.
Diameter, depth and reinforcement come from your plan or building department. Use the tool to convert approved sizes into a quantity, not to decide what size is adequate.
12 inches is a common diameter for residential deck footings, but the correct size depends on the load the footing carries and local soil bearing capacity -- check your local building code or an engineer's spec.
Deep enough to sit below your local frost line, which building departments publish for your region -- shallow footings can heave with seasonal freeze-thaw cycles.
Not in a single calculation -- run the calculator once per unique size, then add the resulting volumes together for your total order.
Run the calculator once for each size and add the volumes together for your total order.
No. It measures only the concrete inside the form. If you pour without a tube, the hole size determines the volume, so use the hole diameter.
That depends on the yield printed on the bag, which varies by product, so divide the volume by the yield stated on your chosen bag.