🏗️Sonotube Concrete Calculator

A Sonotube is a brand name for a heavy-duty cardboard tube used as a form for pouring concrete columns, piers, footings, and other cylindrical structures.

Measure the inside diameter of the tube, as this will be the diameter of your concrete pier. Common sizes range from 6 inches to 36 inches or more.

The height depends on your project requirements, such as deck height, frost line depth, and structural load. Ensure it extends below the frost line and to the required elevation.

An 80lb bag of standard concrete mix typically yields about 0.60 cubic feet of concrete. A 60lb bag yields about 0.45 cu ft, and a 40lb bag about 0.33 cu ft. This calculator uses these estimates.

Yes, often a wider base or “bell footing” is created at the bottom of the pier for better stability and load distribution. This calculator estimates volume for the tube itself; additional volume for a flared base needs separate calculation.

The number of piers depends on the size and design of the structure you are supporting (e.g., deck, shed). Consult building plans or a structural engineer.

Concrete typically reaches a good portion of its strength in 7 days and continues to cure for about 28 days. Forms can often be removed after 24-48 hours, depending on conditions, but load should not be applied until sufficient curing.

For structural piers, reinforcement with rebar (steel reinforcing bars) is almost always necessary to provide tensile strength. Consult local codes or an engineer for rebar requirements.

Yes, Sonotubes can be easily cut to the desired length using a handsaw or circular saw.

Tubes should be set plumb (vertically). If the ground is sloped, you may need to excavate to create a level base for each tube, or cut tubes to different lengths to achieve a level top across all piers.