Round cardboard tube forms such as Sonotube are used for deck footings, piers and columns. Enter the tube diameter, the depth or height and how many tubes you will pour; the calculator gives the concrete volume and the number of bags.
Sonotube formula
Volume of one tube (cu ft) = π × (diameter in inches ÷ 24)² × height in feet Total = volume per tube × number of tubes Bags = total ÷ bag yield (80 lb = 0.60 cu ft, 60 lb = 0.45, 40 lb = 0.30)
Worked example: six 12 in tubes, 4 ft deep
- One tube: π × 0.5² × 4 = 3.14 cu ft.
- Six tubes: 18.85 cu ft (0.7 cu yd).
- 80 lb bags at 0.60 cu ft each: 32 bags.
Concrete per foot of tube
| Diameter | Cu ft per ft | 80 lb bags per ft |
|---|---|---|
| 6 in | 0.196 | 0.33 |
| 8 in | 0.349 | 0.58 |
| 10 in | 0.545 | 0.91 |
| 12 in | 0.785 | 1.31 |
| 14 in | 1.069 | 1.78 |
| 16 in | 1.396 | 2.33 |
| 18 in | 1.767 | 2.95 |
| 24 in | 3.142 | 5.24 |
Bag yields are from the QUIKRETE Concrete Mix data sheet. If the hole below the tube is wider than the tube, or you add a bell footing, calculate that part separately and add it. Past about 1 cubic yard, ready-mix is usually easier than bags.
Questions
How many bags of concrete for a 12 in Sonotube?
About 1.31 80 lb bags per foot of depth, so 6 bags for a 4 ft tube.
How many bags for an 8 in tube 4 ft deep?
3 bags of 80 lb.
Is this different from the post hole calculator?
Yes. The post hole calculator subtracts the post from a hole; this one fills an empty round form.
Sources
- QUIKRETE Concrete Mix (No. 1101) data sheet, QUIKRETE.
Used for: Yields of 0.60, 0.45 and 0.30 cu ft for 80, 60 and 40 lb bags.