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Concrete Column Calculator

Get cubic yards and bag counts for round tube-form or square concrete columns and piers.

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Count the hole, not just the tube

When a tube form sits in an augered hole, the gap between the tube and the soil, plus any bell or pad at the bottom, also fills with concrete if it is not backfilled first. Backfill and tamp around the tube before the pour, or add the extra volume to your count.

How to calculate concrete for a column or pier

A round column is a cylinder, so its volume is π × radius² × height. With the diameter in inches, divide by 12 to get feet and by 2 for the radius. A 12-inch tube 4 ft tall holds π × 0.5² × 4 = 3.14 cu ft, a little over five 80 lb bags. A square column is simply width × width × height.

Tube size has a large effect because volume grows with the square of the diameter. An 8-inch tube holds about 0.35 cu ft per foot of height, a 10-inch about 0.55, a 12-inch about 0.79 and a 16-inch about 1.40. Doubling the diameter roughly quadruples the concrete.

Because cardboard tube forms hold their shape, a 5 percent allowance usually covers spillage and slight overfill. If the tube sits on a wider footing pad or a bell-shaped base, or the hole below the tube is dug oversize, calculate that part separately and add it; an irregular hole can take far more concrete than the tube.

Small column jobs are almost always done with bagged mix. The counts use 0.60 cu ft per 80 lb bag and 0.45 cu ft per 60 lb bag, and the per-column figure helps you stage the right number of bags beside each hole before you start mixing.

Where these numbers come from

The formulas and default values in this calculator are based on:

  • QUIKRETE Concrete Mix No. 1101 technical data sheet (80 lb bag yields about 0.60 cu ft, 60 lb about 0.45 cu ft)
  • standard cylinder volume formula

These are planning estimates. Check product labels, your local building code, and a licensed contractor before you buy materials or build.

Frequently asked questions

How many bags of concrete fill a 12-inch Sonotube?

About 0.79 cu ft per foot of height, which is roughly 1.3 bags of 80 lb mix per foot. A 4-ft-tall 12-inch column takes about 5.2 bags, so plan on 6 per column if you are pouring one at a time.

Should I use round or square columns?

Round tube forms are faster to set and brace and use about 21 percent less concrete than a square column of the same width. Square columns need built wood forms but can be easier to match to square posts or masonry.

Does this include the footing under the column?

No. It calculates the column itself. If your plan calls for a spread footing pad below the column, calculate the pad with the rectangular option in the concrete calculator and add it to this total.

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