Sonotube Calculator
How much concrete fills a Sonotube? Volume, 40/60/80 lb bags and cubic yards for round column forms and deck footings, any size.
Your estimate
24 bags
80 lb bags (incl. 10% waste)
- Concrete volume (incl. waste)
- 13.82 cu ft (0.51 cu yd)
- Per column
- 3.14 cu ft · 6 bags
- Total weight
- 1,920 lb
- Form tubes
- 4
Other sizes for comparison
- 60 lb bags
- 31
- 40 lb bags
- 47
Show the math
- Volume per column = π × (diameter ÷ 2)² × height = 3.14 cu ft
- × 4 columns = 12.57 cu ft; × (1 + 10%) = 13.82 cu ft
- ÷ 0.6 cu ft per bag = 23.04 → 24 bags
Shopping list & cost
| Item | Spec | Qty | Cost |
|---|---|---|---|
| Premix concrete | 80 lb bag | 24 bags | — |
| Concrete form tube | 12 in × 4 ft | 4 | — |
| Post anchors / J-bolts | per your post or beam connector | 4 | — |
Prices are what you enter under Advanced options. Estimates only — check stock and pricing with your supplier.
Quick answer Four 12 in Sonotubes 4 ft tall hold 3.14 cu ft each, 13.82 cu ft in total with 10% waste — 24 bags of 80 lb premix. A 12 in tube holds 0.785 cu ft per foot of height, about 1.3 × 80 lb bags. Four 300 mm tubes 1.2 m tall need 40 bags of 20 kg mix. Volume = π × (diameter ÷ 2)² × height.
Method & assumptions
Volume per column = π × (Diameter ÷ 2)² × Height Total = Volume per column × Number of columns × (1 + waste %) Bags = Total ÷ yield per bag, rounded up cu yd = cu ft ÷ 27
- Diameter
- inside diameter of the form tube
- Height
- full length of concrete in the tube, below and above grade
- Yield per bag
- ~0.30 cu ft (40 lb), 0.45 (60 lb), 0.60 (80 lb) — check the label
Assumptions & limits
- Straight cylinders; bell or spread footings at the bottom are not included — add them as a separate volume.
- Bag yields are typical label values for standard premix.
- Footing size and depth come from your plans, the AWC DCA 6 guide for decks or local code — this tool only computes concrete.
Rounding: purchase quantities are always rounded up to whole units as sold. See our methodology.
Diagram
How to use this calculator
- Enter the inside diameter of the tube: 8, 10 and 12 in are the usual sizes for deck and porch footings.
- Enter the full column height — the depth in the ground plus any part above grade.
- Enter how many identical columns you are pouring.
- Keep 10% waste: holes are rarely perfectly round and the bottom often flares wider than the tube.
- Pick the bag size; above about 1 cu yd, price a ready-mix or mini-mix delivery instead.
Worked examples
Imperial: 6 deck footings, 10 in tubes, 42 in deep
- Per tube = π × (5 in)² × 42 in = 3,299 in³ = 1.91 cu ft
- × 6 = 11.45 cu ft; +10% = 12.6 cu ft
- ÷ 0.6 = 21 → 21 bags of 80 lb
Metric: 3 porch posts, 250 mm tubes, 900 mm
- Per tube = π × 0.125² × 0.9 = 0.0442 m³ (44 L)
- × 3 = 0.133 m³; +10% = 0.146 m³
- ÷ 9.4 L = 15.5 → 16 × 20 kg bags
In depth: sonotube planning notes
Sizing the footing and the hole
A Sonotube is only a form — the footing size is set by the load and the soil. For decks, the American Wood Council's DCA 6 guide lists footing sizes by joist span, beam span and soil bearing capacity, and requires the bottom of the footing to be at least 12 in below undisturbed grade and below the local frost depth. Many builders use a wider footing pad or a plastic bell form at the bottom of the tube to spread the load, then a smaller tube above. Calculate the bell or pad as a separate volume and add it to the tube total.
Dig the hole a few inches wider than the tube so you can plumb and backfill it, and keep the bottom flat and undisturbed. Where the hole bells out at the bottom, the concrete fills that too, which is one reason the default waste is 10%. In clay, loose soil or high water tables, ask your building department — some require inspections of the open holes before the pour.
Pouring the columns
Cut each tube to length so the top sits at the planned height, brace it plumb with stakes and screws, and backfill around it in lifts before pouring so the tube doesn't float or shift. For a handful of footings, bagged premix mixed in a wheelbarrow or a small mixer is practical: a 12 in tube 4 ft tall takes five or six 80 lb bags. For a dozen or more, a mini-mix or ready-mix truck with a chute or pump saves a day of heavy work and gives a more consistent pour.
Fill in stages and rod each lift with a piece of rebar or tap the side of the tube to release trapped air. Strike the top flat or slightly crowned, and set the post base, anchor bolt or J-bolt immediately, checking position with a string line. Leave the tube in place until the concrete has cured, then strip any exposed cardboard. If the columns carry significant loads, your plans may call for vertical rebar in each tube.
Reference table
| 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 |
Key facts
- 12 in × 4 ft tube
- 3.14 cu ft ≈ 5.2 × 80 lb bags
- 1 cu yd fills
- ≈ 34 ft of 12 in tube
- Footing depth
- below local frost line; DCA 6: at least 12 in below grade
Tips & common mistakes
- Call 811 before you dig — locating buried utilities is free in the US.
- Brace tubes plumb and check the tops with a string line before pouring; cut tubes to height first.
- Rod or tap the tube as you fill to work out air pockets, and set post bases or J-bolts while the concrete is wet.
- Peel the cardboard off any part that will be exposed once the concrete has cured.
Frequently asked questions
How many bags of concrete for a 12 inch Sonotube?
Each foot of a 12 in tube holds 0.785 cu ft, about 1.3 × 80 lb bags. A 4 ft tube takes about 5.2 bags — buy 6.
How many bags of concrete for an 8 inch Sonotube?
0.349 cu ft per foot: about 0.6 × 80 lb bags per foot, so a 4 ft tube needs about 2.3 bags — buy 3.
How deep should a Sonotube footing be?
Below your local frost depth, and per the AWC DCA 6 deck guide at least 12 in below undisturbed grade. Your building department sets the local depth.
What size Sonotube for a deck?
8–12 in tubes are common for residential decks, often with a wider footing pad at the bottom. Footing size depends on load and soil — follow DCA 6 or your plans.
Can I use bagged concrete in a Sonotube?
Yes. For a few footings, 60 or 80 lb bags of standard mix are typical. Above about 1 cu yd, a ready-mix or mini-mix truck is usually cheaper.
Sources
- American Wood Council – DCA 6 Prescriptive Residential Wood Deck Construction Guide — general reference — not cited for a specific figure
- Sonoco – Sonotube concrete forms — general reference — not cited for a specific figure
- Quikrete – Concrete Mix (No. 1101) product data sheet — accessed : “40 lb ≈ 0.30 ft³, 60 lb ≈ 0.45 ft³, 80 lb ≈ 0.60 ft³ (17 L) per bag”
Default values (yields, coverage rates and densities) are typical figures from manufacturer literature. Always check the label on the product you buy.
Related calculators
- Concrete Bag CalculatorHow many bags of concrete do you need? Compare 40, 60 and 80 lb or 20, 25 and 30 kg bags, total weight and cost — with the math shown.
- Deck Board CalculatorWork out how many deck boards, joists, screws or hidden clips you need for a deck, using real board widths, gaps and stock lengths.
- Concrete Slab CalculatorEstimate cubic yards and bags for a slab or patio, including a 12×12 ft pad at 4 in, with waste, the formula and a shopping list.
Learn more in our guides
Method, waste and worked examples: Concrete volume: formulas, waste and examples.
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DIYCalcLab. “Sonotube Calculator.” Oct 19, 2026. https://diycalclab.com/concrete/sonotube-calculator/
Estimates only. Verify quantities with your supplier and local building codes. For structural, electrical or safety-critical work, consult a licensed professional. Full disclaimer.