Find out how much concrete you need to fill round tube forms for piers, footings, and posts. Get cubic feet, cubic yards, and bag counts.
0cu ft
| Item | Amount |
|---|---|
| Per tube | |
| Cubic yards | |
| 40 lb bags | |
| 50 lb bags | |
| 60 lb bags | |
| 80 lb bags |
A round concrete form is a cylinder, so its volume is the area of the circle times the height.
Volume = π × (diameter ÷ 2)² × length
The calculator finds the volume of one tube, multiplies it by the number of tubes, adds your extra allowance, and converts to cubic yards and to bags. Bag counts are rounded up.
| Diameter | Cu ft per foot |
|---|---|
| 8 in | 0.35 |
| 10 in | 0.55 |
| 12 in | 0.79 |
| 16 in | 1.40 |
| 18 in | 1.77 |
| 24 in | 3.14 |
Yields vary slightly by brand, so check the label. For bigger jobs, around 1 cubic yard or more, ready-mix delivery is usually easier and cheaper than bags.
Sonotube is a registered trademark of Sonoco. This site is not affiliated with Sonoco. The calculator works for any round concrete tube form.
A 12 inch tube holds about 0.79 cubic feet per foot of length, so a 4 foot pour takes about 3.14 cubic feet. That is roughly 5 bags of 80 lb concrete, or 6 bags with a 10 percent allowance.
With 10 percent extra, about 6 bags of 80 lb, 8 bags of 60 lb, 10 bags of 50 lb, or 12 bags of 40 lb.
Divide by 27. For example, 54 cubic feet is 2 cubic yards.
Bags are easier for a few small tubes. For roughly 1 cubic yard or more, which is more than 40 bags of 80 lb, a delivered truck usually saves time and money. Check for short-load fees.
Yes. Enter the footing's diameter and depth. Size, depth below the frost line, and rebar come from your plans and local code.