Sonotube sizes chart: diameters, lengths and concrete per tube
Sonotube is Sonoco’s brand of round fiber concrete form, and the name has become shorthand for any cardboard tube used to pour piers, footings and columns. This chart lists the standard sizes and how much concrete each one holds, so you can buy the right tubes and the right number of bags in one trip.
Standard sizes and lengths
- Sonotube round forms: diameters from 6 to 36 in, standard length 12 ft (custom lengths available), per Sonoco’s round-form brochure.
- Sonotube commercial forms: diameters up to 60 in in 12 and 20 ft lengths.
- Sonotube Builder’s Tube (sold for DIY at home centers): 6, 8, 10 and 12 in diameters in 4, 8 and 12 ft lengths.
- Quikrete QUIK-TUBE: 8, 10 and 12 in in 4 ft lengths, with 10 and 12 ft lengths in some regions.
Diameters are inside diameters, and they step up in 2 in increments in the round-form range. Tubes are cut to length on site with a handsaw, so buy the next length up and trim.
Concrete per foot of tube
| Diameter | Cu ft per foot | Cu yd per foot | 80 lb bags per foot | 60 lb bags per foot |
|---|---|---|---|---|
| 6 in | 0.196 | 0.0073 | 0.33 | 0.44 |
| 8 in | 0.349 | 0.0129 | 0.58 | 0.78 |
| 10 in | 0.545 | 0.0202 | 0.91 | 1.21 |
| 12 in | 0.785 | 0.0291 | 1.31 | 1.75 |
| 14 in | 1.069 | 0.0396 | 1.78 | 2.38 |
| 16 in | 1.396 | 0.0517 | 2.33 | 3.10 |
| 18 in | 1.767 | 0.0655 | 2.95 | 3.93 |
| 20 in | 2.182 | 0.0808 | 3.64 | 4.85 |
| 24 in | 3.142 | 0.1164 | 5.24 | 6.98 |
| 30 in | 4.909 | 0.1818 | 8.18 | 10.91 |
| 36 in | 7.069 | 0.2618 | 11.78 | 15.71 |
Cubic yards for common heights
Sonoco’s brochure tabulates cubic yards for columns of 3, 6, 8, 10, 12, 16 and 20 ft. A few rows for quick reference:
| Diameter | 3 ft | 4 ft | 6 ft | 8 ft | 12 ft |
|---|---|---|---|---|---|
| 8 in | 0.039 | 0.052 | 0.077 | 0.103 | 0.155 |
| 10 in | 0.061 | 0.081 | 0.121 | 0.162 | 0.242 |
| 12 in | 0.087 | 0.116 | 0.175 | 0.233 | 0.349 |
| 16 in | 0.155 | 0.207 | 0.310 | 0.414 | 0.621 |
| 24 in | 0.349 | 0.465 | 0.698 | 0.931 | 1.396 |
The sizes people ask about
- How many bags of concrete for a 12 inch Sonotube — about 6 bags of 80 lb for 4 ft with a little extra.
- How many bags of concrete for a 10 inch Sonotube — very nearly one 80 lb bag per foot.
- How many bags of concrete for an 8 inch Sonotube — about 4 bags of 60 lb for 4 ft.
Choosing a diameter
The diameter of a pier is a structural choice: it depends on the load the post carries, the soil it bears on, and whether the tube sits on a wider footing. Deck plans and building departments specify it, along with the depth (often below the local frost line). The chart only tells you what a given size holds. A 6×6 post set on a pier is a common question — the post-to-tube fit is about the hardware, while the pier size comes from the plans; see how much concrete for a 6×6 post for posts set directly in concrete.
For square or larger columns, the column calculator handles any section — compare a round tube with how much concrete for a 12×12 column. Spread footings under tubes are pads, calculated with the footing calculator.
Tips for tube forms
- Set the tube on firm, undisturbed soil or on the footing, and backfill around it before pouring so it can’t float or bulge.
- Brace it plumb in two directions; check with a level on two faces.
- Fill in lifts and rod each one. A tube 4 ft tall full of concrete has a lot of pressure at the bottom — don’t rush it.
- Peel the cardboard off above grade once the concrete has hardened, for a clean finish.
- Cardboard concrete tube formBudget price
Round fiber tubes form piers, columns and footings above or below grade. Sold in common diameters; cut to length with a handsaw.
See options on Amazon (opens in a new tab) - Post levelBudget price
Straps to a post or tube form and reads plumb in both directions at once, so you can set it while the concrete is still soft.
See options on Amazon (opens in a new tab) - Mortar and concrete mixing tubBudget price
A wide, shallow tub for one or two bags at a time — easier to clean and to pull a hoe through than a wheelbarrow.
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As an Amazon Associate we earn from qualifying purchases. Links to products are affiliate links — they cost you nothing extra and help keep these calculators free.
Frequently asked questions
What sizes do Sonotubes come in at home centers?
Usually the Builder’s Tube sizes: 6, 8, 10 and 12 in diameters in 4 ft lengths, sometimes 8 and 12 ft. Larger round forms up to 36 in come from building suppliers.
How long is a standard Sonotube?
Sonoco’s standard round forms are 12 ft long; DIY Builder’s Tubes come in 4, 8 and 12 ft lengths. Cut them to the height you need.
Sources
- Sonoco — Sonotube round concrete forms brochure (opens in a new tab) — Diameters 6–36 in, 12 ft standard length; cubic yards by height.
- Sonoco — Sonotube commercial concrete forms brochure (opens in a new tab) — Diameters 6–60 in; 12 and 20 ft standard lengths.
- Sonoco — Sonotube Builder’s Tube concrete forms (opens in a new tab) — 6, 8, 10, 12 in; 4, 8, 12 ft; cubic feet and 80 lb bags per foot.
- Quikrete QUIK-TUBE (No. 6922) data sheet (opens in a new tab) — 8, 10, 12 in; 4 ft lengths; bags per tube.
- Quikrete Concrete Mix (No. 1101) data sheet (opens in a new tab) — Bag yields.