Sonotube Calculator
A sonotube calculator finds the concrete for round cardboard form tubes by treating each tube as a cylinder: volume equals pi times the radius squared times the height. Enter the tube diameter, pour depth and the number of tubes below to get the total cubic yards and bag count.
Enter the tube diameter and height to see the concrete.
How Do You Calculate Concrete for a Sonotube?
To calculate concrete for a sonotube, treat the tube as a cylinder and multiply pi by the radius squared by the height. A 12 inch diameter tube has a radius of 6 inches (0.5 ft), so each foot of depth holds pi * 0.5 * 0.5 = 0.785 cubic feet of concrete. For a 4 ft deep tube that is about 3.14 cubic feet, or 0.12 cubic yards. The calculator scales by the number of tubes and converts to 80 lb bags so you order the right amount.
What Size Sonotube Should You Use?
Common sonotube diameters are 8, 10, 12 and 16 inches, chosen by the load: deck posts and light piers often use 8 to 12 inch tubes, while heavier columns use 16 inches or more. Tube length is cut to depth on site, and the pour depth depends on your frost line and footing design. The calculator handles any diameter and depth you enter so you can size the concrete to your engineered plan.
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Frequently asked questions
- How much concrete for a 12 inch sonotube?
- A 12 inch sonotube holds about 0.785 cubic feet of concrete per foot of depth. A 4 ft deep tube needs about 3.14 cubic feet, or roughly 6 of the 80 lb bags.
- How do you calculate sonotube concrete?
- Use the cylinder formula: pi times the radius squared times the height. Convert inches to feet first. The calculator does this for any tube size and pour depth.