Concrete per foot of tube (computed by this calculator)
| Diameter | cu ft per ft | 80 lb bags per ft | 60 lb bags per ft |
|---|---|---|---|
| 6 in | 0.196 | 0.33 | 0.44 |
| 8 in | 0.349 | 0.58 | 0.78 |
| 10 in | 0.545 | 0.91 | 1.21 |
| 12 in | 0.785 | 1.31 | 1.75 |
| 14 in | 1.069 | 1.78 | 2.38 |
| 16 in | 1.396 | 2.33 | 3.10 |
| 18 in | 1.767 | 2.95 | 3.93 |
| 24 in | 3.142 | 5.24 | 6.98 |
Worked example
Four 10 in tubes, each filled 48 in: π × 5² × 48 = 3,770 in³ ÷ 1,728 = 2.18 cu ft per tube, 8.73 cu ft in total. With 80 lb bags at 0.60 cu ft: 8.73 ÷ 0.60 = 14.5, so 15 bags (1,200 lb).
Common mistakes
- Using the nominal tube length instead of the height you actually fill.
- Forgetting the part above grade when the tube sticks out of the hole.
- Mixing up bag weight and yield: an 80 lb bag makes 0.60 cu ft, not 0.80.
- Skipping a footing pad where your plans call for a wider base under the tube.
Frequently asked questions
How many bags of concrete for a sonotube?
Multiply π × radius² × height (in inches), divide by 1,728 for cubic feet, then divide by the bag yield. A 10 in × 48 in tube holds 2.18 cu ft: 3.6 bags of 80 lb mix (0.60 cu ft) or 4.8 bags of 60 lb (0.45 cu ft).
How much concrete does a 12 inch sonotube hold per foot?
π × 6² × 12 ÷ 1,728 = 0.785 cu ft per foot of height, about 1.3 bags of 80 lb mix per foot.
Should I round bags per tube or for the whole job?
If you mix and pour continuously, round the job total once. If you mix each tube separately, round each tube up; the calculator shows bags per tube so you can do either.
How deep should a deck footing tube go?
Deck footings must bear below the local frost depth and meet the size in your plans or AWC DCA 6. This calculator only computes the concrete for the height you enter.