Concrete per sonotube size
| Diameter | cu ft per ft | cu ft in 4 ft | 80 lb bags in 4 ft |
|---|---|---|---|
| 6 in | 0.20 | 0.79 | 2 |
| 8 in | 0.35 | 1.40 | 3 |
| 10 in | 0.55 | 2.18 | 4 |
| 12 in | 0.79 | 3.14 | 6 |
| 14 in | 1.07 | 4.28 | 8 |
| 16 in | 1.40 | 5.59 | 10 |
| 18 in | 1.77 | 7.07 | 12 |
| 24 in | 3.14 | 12.57 | 21 |
Before extra for waste.
How to calculate concrete for a round form
π × (diameter in inches ÷ 24)² × height in feet = cubic feet
12 in tube, 4 ft high: 3.1416 × 0.5² × 4 = 3.14 cu ft
If the tube sits on a wider footing, such as a bell-shaped base or a square pad, work that out separately with the footing calculator and add the two together.
Tips for pouring sonotubes
- Brace each tube plumb before pouring. Wet concrete can push a loose tube off line.
- Pour in stages and rod or tap the sides to remove air pockets.
- Set anchor bolts or post bases while the concrete is still wet.
Common questions
How many bags of concrete fill a 12 inch sonotube?
A 12 in tube holds about 0.79 cubic feet per foot of height. A 4 ft tube needs about 6 bags of 80 lb.
How many bags for an 8 inch sonotube?
An 8 in tube holds about 0.35 cubic feet per foot. A 4 ft tube needs about 3 bags of 80 lb.
What size sonotube do I need for a deck?
Deck footings commonly use 8 to 12 in tubes, but the right size depends on the deck's load and your soil. Your local building code or permit drawings will set the minimum.