Sonotube Concrete Calculator
Pick your tube diameter, set the depth and the number of tubes, and read off yards and bags. Works for Sonotube, Quik-Tube, and any round form.
Concrete per tube, per foot of depth
| Diameter | Cu ft per ft of depth | 80 lb bags per ft |
|---|---|---|
| 8" | 0.35 | 0.6 |
| 10" | 0.55 | 0.9 |
| 12" | 0.79 | 1.3 |
| 16" | 1.40 | 2.3 |
| 18" | 1.77 | 2.9 |
| 24" | 3.14 | 5.2 |
The formula
π × radius² × depth, all in feet, divided by 27 for cubic yards. A 12" tube has a 0.5 ft radius, so each foot of depth is π × 0.25 ≈ 0.785 cu ft. Order 10% extra — tubes sit in dug holes and the bottom rarely matches the catalog volume.
Common questions
How much concrete does a 12 inch sonotube hold?
A 12-inch diameter tube holds about 0.785 cubic feet per foot of depth. At 4 feet deep that's 3.14 cu ft — roughly six 80 lb bags, or 0.12 cubic yards per tube.
How many bags of concrete per sonotube?
Per foot of depth: an 8" tube takes about 0.6 bags (80 lb), a 10" tube about 0.9, a 12" tube about 1.3, and a 16" tube about 2.3. Multiply by your depth in feet and round up.
Should I mix bags or order ready-mix for sonotubes?
Under roughly one cubic yard total, bags are cheaper and simpler. Past a yard (about 45 × 80 lb bags of mixing), ready-mix delivery starts winning even with the short-load fee — and your back will agree.
How deep should sonotube footings be?
Below the local frost line, on undisturbed soil, typically 36–48 inches in cold climates. Your building department's frost-depth requirement overrides any rule of thumb.