Concrete for a 12-inch Sonotube
A 12-inch round tube holds 0.785 ft³ of concrete per foot of depth. A 4 ft tube takes 6 bags of 80-lb mix or 8 bags of 60-lb mix, with 10% extra.
- Per foot of tube0.785 ft³
- 4 ft tube3.14 ft³
- 80-lb bags (4 ft, +10%)6
- 60-lb bags (4 ft, +10%)8
Concrete needed
3.46 cubic feet
0.128 yd³ · 0.098 m³ · includes 10% extra
You need about 3.46 cubic feet of concrete, or 6 bags of 80 lb mix.
Bags of premix
- 1240 lb bags
- 1050 lb bags
- 860 lb bags
- 680 lb bags
- —20 kg bags
- —25 kg bags
- Before extra0.12 yd³ (3.1 ft³)
- Weight of bags480 lb
- Per hole—
- Ready-mix costAdd a price per yd³
- Bagged costAdd a price per bag
One 80 lb bag makes about 0.60 ft³ (manufacturer's published yield). Bags are rounded up.
Bagged mix makes sense at 0.13 yd³. A ready-mix truck for a load this small would usually come with a minimum-order or short-load charge.
Estimate only, not a quote or engineering advice. Disclaimer
A 12-inch tube is a standard size for deck and porch footings that carry more load or larger posts.
Bags per 12-inch tube by depth
| Depth | ft³ exact | 80-lb bags | 60-lb bags | 50-lb bags |
|---|---|---|---|---|
| 2 ft | 1.57 | 3 | 4 | 5 |
| 3 ft | 2.36 | 5 | 6 | 7 |
| 4 ft | 3.14 | 6 | 8 | 10 |
| 5 ft | 3.93 | 8 | 10 | 12 |
| 6 ft | 4.71 | 9 | 12 | 14 |
The math
For several tubes, set the number of columns in the calculator: it totals the volume before rounding, which can save a bag or two over multiplying the per-tube count. If the tube sits on a wider footing pad, add that as a separate footing.
Planning all the piers of a deck? Measure each tube's depth: when the ground slopes, the tubes on the low side are taller and need more concrete.
Frequently asked questions
How many bags of concrete for a 12-inch Sonotube?
Each foot of a 12-inch tube holds 0.785 ft³. A 4 ft tube takes 3.14 ft³: 6 bags of 80-lb or 8 bags of 60-lb mix, including 10% extra.
How many cubic feet in a 12-inch Sonotube?
0.785 cubic feet per foot of length. Multiply by the depth in feet.
How much concrete for a 12-inch Sonotube 3 feet deep?
2.36 ft³, which is 5 bags of 80-lb or 6 bags of 60-lb mix with 10% extra.
Other tube sizes
Related
Sources
- QUIKRETE: Concrete Mix No. 1101 data sheet (Revised Oct 2022; checked Nov 11, 2026)