Sonotube Concrete Calculator

Determine concrete volume in cubic yards and pre-mixed bag counts for cylindrical deck post piers and footings.

Tube Diameter (Inches)

Pier Depth / Height (Feet) Total length below & above grade

Number of Identical Piers

Bell-Shaped Footing Base

Common Deck Pier Scenarios

Total Concrete Required

0.53 Cu Yd

14.4 cubic feet total

80 lb Bags Needed 25 Bags @ 0.60 cu ft per bag

60 lb Bags Needed 33 Bags @ 0.45 cu ft per bag

Frost Line Rule: Pier bases must extend at least 6 inches below the local frost line (e.g. 36" to 48" in northern climates) to prevent winter frost heaving from lifting and warping your deck.

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How Sonotube Pier Volume Is Calculated

A Sonotube forms a true geometric cylinder. The volume of a cylinder is calculated by multiplying base circle area by height:

Radius in Feet (r) = (Diameter in Inches / 2) / 12
Cylinder Volume (cu ft) = π × r² × Height (ft)
Total Cubic Yards = (Cubic Feet × Number of Piers) / 27

Frequently Asked Questions

How many 80 lb bags of concrete fill a 10-inch Sonotube?

A 10-inch Sonotube has a volume of 0.545 cubic feet per linear foot. A 4-foot deep pier requires 2.18 cubic feet, which takes exactly 4 eighty-pound bags (0.60 cu ft/bag).

When should I order ready-mix concrete instead of bags?

If your project requires more than 1.0 to 1.5 cubic yards (around 45 to 65 eighty-pound bags), mixing by hand or rental mixer becomes grueling labor. Ordering a ready-mix truck is faster and guarantees uniform PSI.

Do I need rebar inside Sonotubes?

Yes. Insert at least two vertical #4 rebar rods centered in the pier extending into the footing base to provide shear resistance against soil freeze-thaw lateral movement.