Concrete Tube Estimator
Enter the diameter and depth of your tube form (Sonotube, concrete column, or round footing) plus the number of columns, and this calculator instantly returns the volume in cubic yards, cubic feet, and cubic metres, the number of premix bags needed in three sizes, the total weight, and an estimated material cost. Switch between imperial and metric units; a waste buffer is included to avoid running short.
What is a concrete tube form (Sonotube)?
A Sonotube (a brand name that has become the generic term for cylindrical concrete forms) is a fibre or cardboard tube used as a temporary mould for poured concrete. They are most commonly used for deck footings, fence posts, sign posts, structural columns, and round pier footings. Once the concrete cures, you peel away the tube and the column holds its shape. Diameters range from 6 inches up to several feet for large structural columns. The tube is placed in a drilled or excavated hole, filled with mixed concrete, and left to set.
How to calculate concrete volume for a tube form
The volume of a cylinder is the area of the circular cross-section multiplied by the height: V = pi x r^2 x h, where r is the inner radius of the tube and h is the fill depth. In practical units: convert the diameter to feet (divide inches by 12), halve it to get the radius, then square it and multiply by pi (3.14159) and the depth in feet. The result is in cubic feet. Divide by 27 to get cubic yards. Always add 5 to 10 percent extra for spillage, voids, and mixing waste. This calculator performs all those steps automatically, including the waste buffer you choose.
Choosing the right bag size
Premix concrete bags come in three common sizes. An 80 lb bag yields approximately 0.60 cubic feet of finished concrete, a 60 lb bag yields about 0.45 cubic feet, and a 40 lb bag yields about 0.30 cubic feet. For a single deck footing, 60 or 80 lb bags are the practical choice. If your project needs more than a quarter cubic yard (about seven cubic feet), pricing ready-mix delivered by truck is worth doing: the per-cubic-yard cost is often lower than buying bags once you count labour for mixing. This calculator shows volume in cubic yards to make that comparison easy.
Tips for a successful pour
Set the tube so the top sits a few inches above grade if you want to prevent frost heave from wicking along the column; cut it flush with grade afterwards. Temporarily brace the tube plumb before pouring. Work the concrete with a rod or vibrator to eliminate air pockets, especially around any rebar you have placed inside. For cold weather, follow ACI 306 guidelines: keep fresh concrete above 50 degrees Fahrenheit (10 degrees Celsius) for at least three to seven days. For warm weather above 90 degrees Fahrenheit (32 degrees Celsius), moisten the tube before pouring to slow surface drying. Let small footings cure at least 24 hours before removing the form tube and applying any load.
Standard Sonotube volume quick-reference
| Diameter | 2 ft deep | 3 ft deep | 4 ft deep | 6 ft deep | 8 ft deep |
|---|---|---|---|---|---|
| 6 in | 0.39 | 0.59 | 0.79 | 1.18 | 1.57 |
| 8 in | 0.70 | 1.05 | 1.40 | 2.09 | 2.79 |
| 10 in | 1.09 | 1.64 | 2.18 | 3.27 | 4.36 |
| 12 in | 1.57 | 2.36 | 3.14 | 4.71 | 6.28 |
| 14 in | 2.14 | 3.21 | 4.28 | 6.42 | 8.56 |
| 16 in | 2.79 | 4.19 | 5.59 | 8.38 | 11.17 |
| 18 in | 3.53 | 5.30 | 7.07 | 10.60 | 14.14 |
| 20 in | 4.36 | 6.54 | 8.73 | 13.09 | 17.45 |
| 24 in | 6.28 | 9.42 | 12.57 | 18.85 | 25.13 |
Volume in cubic feet for a single tube at common diameters and depths, before any waste buffer. One 80 lb bag yields 0.60 ft³.
Frequently asked questions
How many 80 lb bags of concrete do I need for a 10-inch Sonotube 4 feet deep?
A 10-inch diameter tube at 4 feet deep holds about 2.18 cubic feet of concrete. At 0.60 cubic feet per 80 lb bag, you need roughly 4 bags per column, plus any waste buffer. For four columns, order about 16 to 18 bags to account for a 10% waste margin.
What is the formula for concrete tube volume?
V = pi x r^2 x h, where r is the inner radius of the tube in feet (diameter in inches divided by 24) and h is the fill depth in feet. The result is in cubic feet. Divide by 27 for cubic yards. This calculator does those conversions for any diameter and depth you enter.
Should I include a waste buffer when ordering concrete?
Yes. A 10% waste buffer is standard for small pours using premix bags. Waste comes from residue left in the mixer, overfill trimmed from the top of the tube, and any spillage. Ordering slightly more than the theoretical volume is far cheaper than a second trip to the hardware store.
When should I order ready-mix instead of buying bags?
Once your total pour exceeds about half a cubic yard (roughly 13 to 14 cubic feet, or 22 to 24 bags at 80 lb), ready-mix truck delivery is often cheaper when you factor in the cost of labour to mix bags. This calculator shows your volume in cubic yards to help you compare.
Can I use this calculator for non-standard tube diameters?
Yes. Select "Custom" from the diameter preset dropdown and type any inner diameter in inches (or centimetres if you switch to metric). The cylinder volume formula works for any diameter.
How deep should a Sonotube footing be?
Depth depends on local frost depth and load requirements. Most residential deck footings need to extend at least 12 inches below the frost line in cold climates; frost lines range from near zero in the southern US to over 5 feet in northern Canada. Your local building department or permit requirements specify the minimum depth for your area.