Sonotube & Concrete Column Calculator
For round tube forms such as Sonotube, deck piers and round columns. Enter the tube diameter in inches, the height or depth in feet, and how many.
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
How column volume is calculated
A round column is a cylinder: the area of the circle times the height. With the diameter in inches:
Cubic yards = cubic feet ÷ 27
Example: a 12-inch tube 4 ft deep is π × 0.5² × 4 = 3.14 ft³. That is 5.2 bags of 80-lb mix, so buy 6. With 10% extra it is 5.8 bags, still 6.
Concrete per foot of tube
| Tube diameter | ft³ per ft | Feet per ft³ | Feet per 80-lb bag | 80-lb bags per ft |
|---|---|---|---|---|
| 6 in | 0.196 | 5.09 | 3.06 | 0.33 |
| 8 in | 0.349 | 2.86 | 1.72 | 0.58 |
| 10 in | 0.545 | 1.83 | 1.10 | 0.91 |
| 12 in | 0.785 | 1.27 | 0.76 | 1.31 |
| 14 in | 1.069 | 0.94 | 0.56 | 1.78 |
| 16 in | 1.396 | 0.72 | 0.43 | 2.33 |
| 18 in | 1.767 | 0.57 | 0.34 | 2.95 |
| 24 in | 3.142 | 0.32 | 0.19 | 5.24 |
Size-specific tables: 8-inch, 10-inch, 12-inch and 18-inch tubes.
Belled footings and holes wider than the tube
If the tube sits on a wider footing or bell, calculate that part separately (a footing or a short column of the bell's diameter) and add it. Concrete that fills gaps around the tube in an oversized hole also adds up, which is one reason to keep the waste allowance.
Frequently asked questions
How many bags of concrete do I need for a Sonotube?
Multiply the cubic feet per foot of tube by the depth, then divide by the bag yield. An 8-inch tube holds 0.35 ft³ per foot, so a 4 ft tube takes 1.40 ft³: 3 bags of 80-lb mix (0.60 ft³ each). A 12-inch tube 4 ft deep takes 6 bags.
How do I calculate concrete for a round column?
Use π × radius² × height, with the radius and height in feet. A 10-inch column (radius 0.417 ft) that is 3 ft tall holds π × 0.417² × 3 = 1.64 ft³.
What does "Sonotube" mean?
Sonotube is a brand name for cardboard tube forms that has become the everyday word for any round concrete form. The calculation is the same for any brand or for a plain round hole.
Should I add waste for tubes?
A little. The tube itself is accurate, but the hole below or around it rarely is. The calculator adds 10% by default.
Related
Sources
- QUIKRETE: Concrete Mix No. 1101 data sheet (Revised Oct 2022; checked Nov 11, 2026)