Sonotube Concrete Column Calculator
Sonotube calculator for round columns, piers and deck footings. Enter tube diameter and height to get cubic yards, cubic feet per column and bags to buy.
By CalcBuilt Editorial TeamUpdated September 11, 2026Formulas checked against manufacturer specs, see how we calculate.
Results
- Concrete needed
- 0.36 cu yd
- 9.6 cu ft for 4 columns including 10% waste
- Per column
- 2.18 cu ft
- 10 in diameter x 4 ft tall, no waste
- 80 lb bags to buy
- 16 bags
- About 4 bags per column, mixed and placed without a break so the lifts bond
- Approximate weight
- 0.65 tons
- 327 lb per column at 150 lb per cubic foot
Sonotube Concrete Column formula
Cubic feet per column = 3.1416 x (Diameter (in) / 24)² x Height (ft)
Total cubic feet = Per column x number of columns x (1 + waste %)
Cubic yards = Total cubic feet / 27
Bags = Total cubic feet / bag yield (80 lb = 0.60 cu ft, 60 lb = 0.45 cu ft)Worked example
Six 12 in tube forms 3.5 ft tall for a deck: 3.1416 x (12 / 24)² x 3.5 = 2.75 cubic feet per column. 2.75 x 6 = 16.5 cubic feet. Add 10% waste for 18.1 cubic feet, which is 0.67 cubic yards.
In bags: 18.1 / 0.60 = 31 bags of 80 lb mix, or about 5 bags per column. At 150 lb per cubic foot each column weighs about 410 lb.
Quick reference
| Diameter | Cu ft per ft of height | 3 ft tall | 4 ft tall | 5 ft tall |
|---|---|---|---|---|
| 8 in | 0.35 | 2 | 3 | 3 |
| 10 in | 0.55 | 3 | 4 | 5 |
| 12 in | 0.79 | 4 | 6 | 7 |
How to calculate concrete for a round column
A column is a cylinder, so its volume is pi times the radius squared times the height. Work in feet: divide the diameter in inches by 24 to get the radius in feet, square it, multiply by 3.1416 and by the height. A 10 inch column 4 feet tall is 3.1416 x 0.417² x 4 = 2.18 cubic feet, so four of them need 8.7 cubic feet or 0.32 cubic yards.
Cardboard tube forms (Sonotube, Quik-Tube) come in even diameters from 6 to 48 inches; home centers stock 4 foot lengths and lumberyards 12 foot lengths that you cut with a handsaw. Measure the full height from the top of the footing pad or the hole bottom to the top of the pier, not just what shows above grade. Size the diameter to the post base: a Simpson ABU44 fits a 10 inch pier, an ABU66 needs 12 inches so the base is not at the edge.
Bags, mixing and placement
Bagged concrete is the usual choice for columns because each one is a separate small pour with no cold joint between piers. An 80 lb bag yields 0.60 cubic feet, so a 12 inch pier 4 feet tall takes about 5.2 bags, which means buying 6. Add 10 percent for spillage, and buy a bag or two extra: a form that ends up short is hard to top off cleanly later. Above about 20 bags per pier, or 40 piers at 5 bags, call a plant; the truck chute reaches about 16 feet, so a line pump typically adds $600 to $1,000. Order 3,000 psi air-entrained for piers that stand above grade in freeze-thaw country, and do not add water at the chute; a stiff mix rodded in lifts fills a tube fine.
Brace every tube before the pour: stake it plumb with 2x4 kickers on two sides and backfill around it, or the first 200 lb of concrete tilts it. Pour in lifts of 12 to 18 inches and rod each lift to remove air pockets, especially in tubes under 12 inches. Wet-set the post base or a 1/2 inch anchor bolt in the center with 7 inches embedded. Deck piers extend below the frost line (IRC R403.1.4.1) and sit on a wider pad or bell footing sized from IRC Table R507.3.1. The footing calculator sizes that pad.
What this calculator leaves out
The result is concrete for the tubes only. Add the pad or bell footing under each tube and the tube forms themselves, typically $15 to $25 per 12 inch by 4 foot tube in 2026. Post bases or anchor bolts and any #4 dowel tying the pier to its pad are separate as well. Hole digging is separate: a two-man auger rental, or an excavator with a 12 inch bit where there are more than about six piers or the soil is rocky.
Most jurisdictions require a footing inspection with the holes open and the tubes set before you pour, and a second inspection of the post bases and hardware. Permit fees and the gravel at the hole bottom are not included.
Mistakes that cost money
- An unbraced tube floats and tilts once 470 lb of wet concrete goes in; stake it plumb with 2x4 kickers and backfill around it first.
- A 12 in tube bears on 0.79 sq ft; IRC Table R507.3.1 wants a wider pad, so pour a bell or square footing under it.
- A tube standing in groundwater softens and blows out at the bottom; pump the hole and set it on a poured pad or tamped gravel.
- Drilling an anchor into a cured pier near the edge splits it; wet-set the post base or anchor bolt centered while the concrete is plastic.
- Dumping a full tube in one lift traps honeycomb at the bottom where the load lands; place 12 to 18 in lifts and rod each.
- Frost depth is measured at each pier from finished grade to the pad bottom (IRC R403.1.4.1); on a sloped lot the downhill piers go deeper.
Key facts
- A 12 in diameter column uses 0.785 cubic feet of concrete per foot of height, or about 1.3 bags of 80 lb mix.
- An 8 in tube uses 0.35 cubic feet per foot, a 10 in tube 0.55, and a 16 in tube 1.40.
- Doubling the diameter of a column quadruples the concrete: a 16 in pier holds four times as much as an 8 in pier.
- Deck piers are usually 8 to 12 in in diameter and extend below the local frost line.
- A 12 in column 4 ft tall weighs about 470 lb at the standard density of 150 lb per cubic foot.
Frequently asked questions
How many bags of concrete for a 12 inch Sonotube 4 feet tall?
About 3.14 cubic feet, which is 6 bags of 80 lb mix or 7 bags of 60 lb mix, before waste.
How many bags of concrete for an 8 inch Sonotube?
An 8 in tube uses 0.35 cubic feet per foot of height. A 4 ft tube needs 1.4 cubic feet, or 3 bags of 80 lb mix.
Do I need a footing under a Sonotube?
Usually yes. The tube alone bears on less than a square foot, and IRC Table R507.3.1 sizes deck footings from the load and soil. Pour a square pad or use a bell form (Bigfoot, Sonotube Square Foot) under the tube, or dig the hole wider at the bottom.
How deep should deck footings be?
Below the frost line, which your local building department sets. Where there is no frost, at least 12 inches below undisturbed grade.
Sources and references
Next steps for this project
The usual order for a concrete & masonry project. See all concrete & masonry calculators.
Embed this calculator
Results are estimates based on standard formulas and typical product specifications. Confirm quantities with your supplier and local code before ordering.