Sonotube Footing Calculator
Quick answer: Four 10-inch diameter Sonotube forms 48 inches deep hold 2.18 cu ft each — 8.73 cu ft total, or 0.32 cubic yards — which takes 15 eighty-pound bags of concrete mix (16 with 10% waste). Tube volume = pi x (diameter/2)^2 x depth, and bag count = total volume divided by the bag yield, rounded up. Enter your own tube size, depth, and count below for an instant result.
Sonotube cardboard forms make round concrete footings fast, but the volume math is easy to get wrong. Enter the tube diameter, depth, and how many footings you are pouring, and this Sonotube footing calculator gives you the concrete volume in cubic feet and cubic yards plus the 80-lb or 60-lb bag count.
Enter your numbers
Your results
Estimate only. Actual yield varies with mix brand and hole over-dig. Confirm bag yields on your mix package.
How to use this calculator
Enter the Sonotube diameter and depth in inches and how many footings you are pouring. Pick your bag size and adjust the waste allowance — results update instantly.
How it works
Volume per tube = pi x (diameter/2)^2 x depth, divided by 1728 to get cubic feet. Total volume = per-tube volume x number of tubes. Cubic yards = total / 27. Bag count = ceil(total x (1 + waste) / bag yield).
Worked example
10-in diameter, 48-in deep, 4 tubes: per tube = 3.1416 x 25 x 48 / 1728 = 2.18 cu ft; total = 8.73 cu ft = 0.32 cu yd; with 80-lb bags at 0.60 cu ft: 8.73 / 0.60 = 14.55 -> 15 bags exact; 16 bags with the 10% waste allowance (8.7266 x 1.10 / 0.60 = 15.9989 -> 16 bags).
Reference data
| Bag size | Yield (cu ft) |
|---|---|
| 80-lb bag | 0.60 cu ft |
| 60-lb bag | 0.45 cu ft |
Source: Quikrete concrete mix product data (2026) — quikrete.com.
Method & sources
Tube volume is exact cylinder geometry from your entered dimensions. Bag yields come from the manufacturer's product data above; waste % is a user-adjustable planning allowance, and bag counts always round up to whole bags. Results are labeled estimates because real holes are rarely perfect cylinders.
- Concrete-mix bag yields: Quikrete concrete mix product data (2026)
Frequently asked questions
How much concrete does a Sonotube footing need?
Tube volume is pi x radius squared x depth. A 10-inch diameter tube 48 inches deep holds about 2.18 cubic feet; four such tubes need about 8.73 cubic feet, or 0.32 cubic yards - roughly 15 eighty-pound bags.
How many cubic feet does an 80-lb bag of concrete make?
0.60 cubic feet. A 60-lb bag yields 0.45 cubic feet. These figures come from Quikrete concrete mix product data and are shown in the reference table on this page.
Should I add waste when ordering concrete for footings?
Yes. This calculator defaults to 10% waste for hole over-dig, spillage, and uneven tube seating. Bag counts are rounded up to whole bags.
How deep should Sonotube footings go?
Footings must sit below the local frost line, which varies by region - enter the depth your project requires. The calculator does not set the depth for you; it only computes the concrete volume.
Are cubic yards or bag counts more useful for a small job?
For a handful of tubes, bags are cheaper and simpler than a ready-mix delivery. This calculator shows both: cubic yards for delivery comparison and bag counts for the hardware-store run.