Quantity · Round form / Sonotube
Sonotube Concrete Calculator
Calculate concrete volume for round cardboard forms — deck piers, fence posts, and lamp bases. Enter diameter, pour height, and how many tubes you are filling.
Tube dimensions
Yield for this diameter: 0.785 cu ft per foot of height
Concrete needed
0.512cy
13.82 cu ft with waste
- One tube
- 3.14 cu ft
- All tubes (raw)
- 12.57 cu ft
Bag equivalent (80 lb)
24 bags
Under ~1 cy — bags are usually easier than a short-load truck for pier pours.
Breakdown
- π × (12 ÷ 24)² × 4 = 3.14 cu ft per tube
- × 4 tubes = 12.57 cu ft
- × (1 + 10% waste) = 13.82 cu ft
Price data updated . National US ranges from published supplier and contractor averages. Not a bid. Local quotes vary.
How the Sonotube calculator works
A Sonotube is a cylinder. Diameter is given in inches; height in feet. Radius in feet is diameter ÷ 24.
cu ft (one) = π × (diameter_in ÷ 24)² × height_ft cu ft (all) = cu ft (one) × tube_count with waste = cu ft (all) × (1 + waste %) cubic yards = cu ft ÷ 27
Worked example. A 12 in tube 4 ft tall is about 3.14 cu ft (π × 0.5² × 4). With 10% waste plan ~3.5 cu ft — still a bag pour unless you set many piers the same day.
Sonotube yield per foot of height
Volume uses π × (diameter_in ÷ 24)² × height_ft. Waste defaults higher — cylinders spill.
| Diameter | Cu ft / ft height |
|---|---|
| 6" | 0.196 |
| 8" | 0.349 |
| 10" | 0.545 |
| 12" | 0.785 |
| 16" | 1.396 |
Sonotube Concrete calculator FAQ
- How much concrete do I need for a Sonotube?
- Use the cylinder formula: π × (diameter in inches ÷ 24)² × height in feet gives cubic feet for one tube. Divide by 27 for cubic yards. Add about 10% waste — round forms spill at the top and the hole is rarely perfect.
- What diameter Sonotube for a deck post?
- Local code and frost depth control footing size. Many residential deck posts use 8–12 inch tubes; heavier loads and taller posts often need larger diameters or engineered footings. This calculator sizes volume for the tube you choose — it does not replace a structural requirement.
- How deep should I pour a Sonotube footing?
- Pour to the frost line in cold climates, or to the depth your permit specifies. Enter the concrete fill height (often the full buried depth), not just the cardboard stick-up above grade. Bell-shaped bottoms and rebar cages are separate details.
- Should I use bags or ready-mix for Sonotubes?
- A few piers are almost always bag territory. Four 12-inch tubes four feet deep are still well under a cubic yard with waste. Ready-mix makes sense when you combine many piers with a slab pour on the same truck.
- Does the cardboard form stay in place?
- Most Sonotube-style forms are left in place below grade and stripped above grade after the concrete sets, per the manufacturer. Leaving paper above grade can wick moisture and look unfinished — check the product instructions.