Calculate concrete needed to fill Sonotubes. Enter tube diameter, height, and count to get volume in cubic yards or bags.
Sonotubes (round cardboard forming tubes) are the standard method for creating concrete piers for decks, porches, additions, and post-frame buildings. They provide a smooth, uniform cylindrical form that produces clean, consistent piers at an affordable cost.
This calculator determines the exact amount of concrete needed to fill your Sonotubes. Simply enter the tube diameter, height above the footing base, and the number of tubes. The calculator outputs volume per tube and total project volume in cubic feet, cubic yards, and pre-mixed bag equivalents.
Sonotubes come in diameters from 6 to 48 inches, with 8", 10", and 12" being most common for residential deck piers. The tube height depends on your frost depth and how far the pier extends above grade, typically 36–60 inches total.
Accurate calculation of this value helps construction professionals plan projects more effectively, reduce material waste, and ensure compliance with building codes and industry standards. Tracking this metric throughout the project lifecycle helps project managers identify potential issues early and maintain quality standards from foundation to final inspection.
Each Sonotube holds a specific volume of concrete, and miscalculating means either running short mid-pour or having expensive leftover ready-mix. For small pier projects, bags may be more economical; for larger projects, a ready-mix truck is more practical. This calculator helps you decide which approach makes sense. Consistent use of this tool across projects builds a library of reference data that improves estimating accuracy over time and reduces reliance on individual experience alone.
Volume per tube = π × (diameter/2)² × height (in³) Convert to ft³: ÷ 1728 Convert to yd³: ÷ 27 Bags (80-lb): total ft³ ÷ 0.6 Bags (60-lb): total ft³ ÷ 0.45
Result: 1.17 yd³ (53 bags of 80-lb)
Each 12" diameter tube, 48" tall: V = π × 6² × 48 = 5,429 in³ = 3.14 ft³. Six tubes: 18.85 ft³ = 0.70 yd³. Continuing, 18.85 / 0.6 = ~32 bags of 80-lb mix.
6–8" tubes support light structures like pergolas, small sheds, and mail box posts. 10–12" tubes are standard for residential decks and porches. 14–18" tubes handle heavy loads like additions and sunrooms. 24–48" tubes are used for commercial foundations and bridge piers.
Dig the hole 2–4" wider than the tube diameter. Place 4–6 inches of compacted gravel at the bottom for drainage. Set the tube plumb, brace it securely, and backfill around the outside with soil to prevent shifting during the pour.
As a rule of thumb, if total volume exceeds 1 cubic yard (about 45 bags of 80-lb mix), ordering a ready-mix truck saves significant time and labor. A mini-load from most ready-mix plants starts at 1 cubic yard with a small-load surcharge.
Most building codes require 8–12" diameter piers for residential decks, depending on the load each pier supports. 12" is the most common. Check your local code and have an engineer size piers for larger or multi-level decks.
The tube must extend below the local frost line. In northern climates, that's 36–48" or more. In southern states, 12–18" may suffice. The pier also typically extends 6" above grade to keep the structure off the ground.
While not always required by code for small piers, placing one or two lengths of #4 rebar improves tensile and lateral strength significantly. It's inexpensive insurance against cracking.
Yes, for small projects (under 1 cubic yard), hand-mixing bags is practical. An 80-lb bag makes 0.6 ft³, so a 12" tube 48" tall needs about 5–6 bags. For larger projects, a ready-mix truck is faster.
Use a circular saw, reciprocating saw, or hand saw to cut cardboard tubes. Mark the cut line all the way around using a tape measure and a level. A utility knife works for thin-wall tubes.
The portion below grade is typically left in place — it eventually degrades harmlessly. The portion above grade should be stripped (peeled off) within 1–7 days for best appearance.