Sonotube Calculator: Concrete for Round Column Forms
This Sonotube calculator finds the concrete needed to fill round column forms from the tube diameter and pour height. Enter one tube or a whole set of piers to get total cubic yards and bag counts for deck footings, posts, and columns.
Estimated concrete
Estimates only. Add ~5–10% for waste. Bag yields: 40 lb ≈ 0.30, 60 lb ≈ 0.45, 80 lb ≈ 0.60 cu ft. Concrete ≈ 150 lb per cu ft.
How to Use the Sonotube Calculator
- 1
Enter your dimensions
Type the length, width and thickness of your slab, footing or pad and choose your units, feet, inches or meters.
- 2
Get instant volume
See the result in cubic yards, cubic feet and cubic meters, plus weight, the moment you type, no page reloads.
- 3
Buy the right amount
We convert volume into the exact number of 40, 60 and 80 lb bags, truck loads and cost so you order without waste or shortfalls.
The formula
ft³ = π × (Diameter_in ÷ 24)² × Height_ft × qty
- ·Diameter_in = inside form diameter (in)
- ·Diameter_in ÷ 24 = radius converted to feet
- ·Height_ft = pour height of the column (ft)
- ·qty = number of identical tubes
- ·π ≈ 3.14159
A Sonotube is just a cylinder, so its volume is πr²h. Divide the diameter by 24 to turn a diameter in inches into a radius in feet in one step, then multiply by height and the number of tubes.
Worked examples
Example 1: One 12-inch tube, 4 ft tall
- Radius in feet = 12 ÷ 24 = 0.5 ft
- Area = π × 0.5² = 0.785 ft²
- Volume = 0.785 × 4 = 3.14 ft³
- 80 lb bags = 3.14 ÷ 0.60 = 5.24 → 6 bags
Result: About 3.14 ft³, or six 80 lb bags
Example 2: Six 10-inch deck footings, 3.5 ft deep
- Radius in feet = 10 ÷ 24 = 0.4167 ft
- Area = π × 0.4167² = 0.545 ft²
- Per tube = 0.545 × 3.5 = 1.91 ft³
- Total = 1.91 × 6 = 11.45 ft³ = 0.42 yd³
Result: About 11.5 ft³, or roughly 0.42 yd³ for all six
Concrete calculators by project type
Concrete bag yield & coverage
How much mixed concrete a standard bag yields, and how far a cubic yard goes at common slab depths.
| Bag size | Yield (cu ft) | Bags per cubic yard |
|---|---|---|
| 40 lb | 0.30 | 90 |
| 60 lb | 0.45 | 60 |
| 80 lb | 0.60 | 45 |
- 40 lb
- 60 lb
- 80 lb
Related guides
Sonotube Concrete FAQs
How much concrete does a 12 inch Sonotube hold?
A 12-inch diameter tube holds about 0.785 cubic feet per foot of height, so a 4-foot tube needs roughly 3.1 cubic feet, or about five 80 lb bags.
How do I calculate concrete for a Sonotube?
Multiply pi by the radius squared by the height in feet to get cubic feet, then divide by 27 for cubic yards. A 10-inch tube 4 feet tall is about 2.18 cubic feet.
How many bags of concrete for a Sonotube footing?
It depends on diameter and depth. An 8-inch tube 4 feet deep needs about 1.4 cubic feet, or roughly two to three 80 lb bags per pier.
What size Sonotube do I need for a deck post?
Deck footings commonly use 8, 10, or 12 inch tubes depending on load and local code; larger loads and taller posts call for wider tubes.
Should I add a footing base under the Sonotube?
Many footings include a wider bell or a poured pad at the base for bearing; add that volume separately since the tube only accounts for the column itself.
How much extra concrete should I order for Sonotubes?
Add about 10 percent, since tubes can bulge slightly under the weight of fresh concrete and holes are rarely perfectly sized.
How much concrete does an 8-inch Sonotube hold per foot?
Using π × (8 ÷ 24)², the cross-section is about 0.349 ft², so each foot of height holds roughly 0.35 ft³. A 4-foot pour is about 1.4 ft³, or three 80 lb bags. Multiply the per-foot figure by your actual depth to size the pour.
How deep should a Sonotube go?
Set the base of the tube below your local frost line so the footing does not heave in winter, which is commonly 36 to 48 inches in cold climates. Check your building code for the exact depth. The calculator uses your entered height, so measure from the bottom of the hole to the top of the form.
Can I cut a Sonotube to length?
Yes, Sonotubes cut easily with a handsaw or reciprocating saw. Measure the total pour height, cut square so the top sits level, and brace the tube plumb before pouring. Cutting to the exact height also avoids wasting concrete filling extra form length.
How many 80 lb bags fill a 12-inch by 4-foot Sonotube?
That tube holds about 3.14 ft³. At 0.60 ft³ per 80 lb bag, you need 3.14 ÷ 0.60 = 5.24, so round up to six bags. Buy an extra bag as a buffer since bag yield varies slightly with how wet you mix it.
Do I remove the Sonotube form after pouring?
The tube can stay in place below grade, but any cardboard left above ground should be peeled off after the concrete sets to prevent it soaking up water and deteriorating. Strip the exposed portion within a day or two while it peels cleanly. Below-grade sections will simply rot away harmlessly over time.
How do I keep a Sonotube from floating or shifting?
Backfill and tamp soil evenly around the tube, and brace it plumb with stakes and 1x4s on two sides before pouring. Pour in lifts and consolidate with a rod or vibrator to avoid pushing the form sideways. A footing base such as a Bigfoot also anchors the bottom against uplift.
What is the difference between a Sonotube and a Bigfoot form?
A Sonotube is the round column form; a Bigfoot is a bell-shaped plastic footing base that snaps onto the bottom of the tube to spread the load over a wider area. Using both gives you a footing and pier in one monolithic pour. Add the base volume separately, as this calculator only sizes the cylindrical tube.