Sonotube Volume Calculator — Cylinder Cubic Feet
Compute concrete volume for any cylindrical Sonotube form. Returns cubic feet, cubic yards, and both 60 and 80-pound bag counts at any tube diameter and depth.
Enter Dimensions
Depth below grade to bottom of footing
Results
Bags per Tube
5bags
Total Bags
20bags
Volume per Tube
2.18cu ft
Concrete volume for one tube
Total Volume
0.323cu yd
All tubes combined
Editorial Standards
Each calculator is reviewed for formula accuracy, unit consistency, and alignment with current U.S. building practices before publication. We verify outputs against published engineering references and real-world project data. Learn more about our methodology.
Sonotube volume calculation is straightforward geometry: π × radius² × height. The math doesn't change whether you're estimating a 4-inch garden post or a 24-inch commercial pier; only the dimensions vary.
This calculator handles any cylindrical concrete volume calculation. Output is in cubic feet (for bag-mix planning) and cubic yards (for ready-mix delivery). For specific applications, see related calculators in the Sonotube cluster.
How to Calculate Sonotube Volume
Volume (cu ft) = π × (D ÷ 24)² × Depth (ft) × 12. Cubic yards = cu ft ÷ 27. 80 lb bags = cu ft ÷ 0.60.
Sonotube Volume Quick Reference
- 6″ × 4 ft: 0.79 cu ft (2 bags 80 lb)
- 8″ × 4 ft: 1.40 cu ft (3 bags 80 lb)
- 10″ × 4 ft: 2.18 cu ft (4 bags 80 lb)
- 12″ × 4 ft: 3.14 cu ft (6 bags 80 lb)
- 14″ × 4 ft: 4.28 cu ft (8 bags 80 lb)
- 16″ × 4 ft: 5.59 cu ft (10 bags 80 lb)
- 18″ × 4 ft: 7.07 cu ft (12 bags 80 lb)
- 24″ × 4 ft: 12.57 cu ft (21 bags — consider ready-mix)
Frequently Asked Questions
How do I calculate the volume of a Sonotube?
Volume = π × radius² × height. For a 10 inch Sonotube 4 ft deep: π × (10/2/12)² × 4 = π × 0.1736 × 4 = 2.18 cubic feet. Convert to cubic yards by dividing by 27.
Why is volume measured in cubic feet for Sonotubes?
Concrete bags are sold by yield in cubic feet (60 lb bag = 0.45 cu ft, 80 lb = 0.60 cu ft). For ready-mix delivery, the unit shifts to cubic yards. Both conversions are straightforward.
Does the volume include the Sonotube form itself?
No — Sonotube cardboard is just the form. The volume calculation is the interior space being filled with concrete. The cardboard adds ~1/4 inch to the outside diameter but is irrelevant to the concrete volume.
How is the depth measured?
Depth is the total length of the tube being filled, typically from the bottom of the hole to about 1-2 inches above grade. The exposed portion above grade is included since it gets filled too.
What if my hole is wider than the Sonotube?
Standard practice: dig hole 2 inches wider than tube, place tube centered with the annular space backfilled with gravel. Concrete volume is calculated for the TUBE only, not the hole. Don't confuse these two volumes.
Looking for the general calculator?
Calculate concrete volume and bags needed to fill Sonotube forms for deck posts and piers. Supports 6, 8, 10, and 12-inch diameter tubes at any footing depth.
Open the Sonotube Calculator: Bags Per Footing →