Cylinder volume, step by step
A round column is a cylinder. Volume = π × r² × h, where r is the radius (half the diameter). The calculator converts the diameter from inches to feet first:
- 12 in diameter ÷ 12 = 1 ft, so the radius is 0.5 ft.
- 0.5² × 3.1416 = 0.785 ft² cross-section.
- × 4 ft height = 3.14 ft³ per column.
- × number of columns, plus waste, then ÷ 27 for cubic yards or ÷ bag yield for bags.
Tube forms are sold by inside diameter, which is what concrete fills, so use that number.
Tube form concrete chart
Volume per foot of height for common tube diameters, with the bags needed for a 4 ft tall tube. Numbers come from the calculator with no waste.
| Tube diameter | ft³ per foot of height | 80 lb bags per 4 ft tube | 60 lb bags per 4 ft tube |
|---|---|---|---|
| 6 in | 0.2 | 2 | 2 |
| 8 in | 0.35 | 3 | 4 |
| 10 in | 0.55 | 4 | 5 |
| 12 in | 0.79 | 6 | 7 |
| 14 in | 1.07 | 8 | 10 |
| 16 in | 1.4 | 10 | 13 |
| 18 in | 1.77 | 12 | 16 |
| 24 in | 3.14 | 21 | 28 |
| Tube diameter | Litres per metre of height | 40 kg bags per 1.2 m tube | 25 kg bags per 1.2 m tube |
|---|---|---|---|
| 15 cm | 17.7 | 2 | 2 |
| 20 cm | 31.4 | 3 | 4 |
| 25 cm | 49.1 | 4 | 6 |
| 30 cm | 70.7 | 5 | 8 |
| 35 cm | 96.2 | 7 | 10 |
| 40 cm | 125.7 | 9 | 13 |
| 45 cm | 159 | 11 | 17 |
| 60 cm | 282.7 | 19 | 29 |
Volume grows with the square of the diameter: a 16 in tube holds about 1.8 times as much as a 12 in tube, not 1.3 times.
Worked examples
Deck: eight 10 in piers, 42 in deepDeck: eight 25.4 cm piers, 107 cm deep
Diameter 10 in · Height 3.5 ft · Number of columns 8 · Waste / overage 5 %Diameter 25.4 cm · Height 1.07 m · Number of columns 8 · Waste / overage 5 %
- Concrete volume: 0.59 yd³ (16 ft³)Concrete volume: 0.454 m³ (454 L)
- 80 lb bags: 2740 kg bags: 25
Carport: six 12 in columns, 4 ftCarport: six 30.5 cm columns, 1.22 m
Diameter 12 in · Height 4 ft · Number of columns 6 · Waste / overage 5 %Diameter 30.5 cm · Height 1.22 m · Number of columns 6 · Waste / overage 5 %
- Concrete volume: 0.73 yd³ (19.8 ft³)Concrete volume: 0.56 m³ (560 L)
- 80 lb bags: 3340 kg bags: 30
- 60 lb bags: 4425 kg bags: 48
Pole barn: twelve 16 in piers, 4 ftPole barn: twelve 40.6 cm piers, 1.22 m
Diameter 16 in · Height 4 ft · Number of columns 12 · Waste / overage 5 %Diameter 40.6 cm · Height 1.22 m · Number of columns 12 · Waste / overage 5 %
- Concrete volume: 2.61 yd³ (70.4 ft³)Concrete volume: 1.99 m³
- 80 lb bags: 11840 kg bags: 107
At around 2 cubic yards, consider ready-mix with a chute or a wheelbarrow crew.At around 1.53 m³, consider ready-mix with a chute or a wheelbarrow crew.
Tubes with a wider base
Many piers flare out at the bottom, either with a plastic footing form (bell) or with a square pad poured first. Calculate the two parts separately:
- Tube section: this calculator, using the tube height above the base.
- Square pad: the footing calculator with one pad.
- Plastic bell forms: the manufacturer lists the bell's volume. Add it to the tube volume.
Practical notes
- Brace tubes plumb and backfill around them partway before pouring. Wet concrete is heavy enough to tip or bulge an unsupported tube.
- Fill in lifts and rod or tap the sides to release trapped air.
- Set anchor bolts or post bases while the concrete is still workable, and check their height and alignment with a string line.
- Pier depth and diameter for decks and structures come from code or an engineer. In cold climates the bottom must be below frost depth.
- Waste on tube pours is small. 5% covers spillage and the cone of concrete you can't scrape out of the mixer.
How deep and how wide should piers be?
Two things set pier depth: frost and load. In cold climates, the bottom of a structural pier must sit below the local frost depth so freezing soil can't lift it. Quikrete's post guidance says at least 6 in below the frost line for structural posts. The diameter is driven by the load the pier carries and how much weight the soil can bear. Prescriptive deck guides such as the American Wood Council's DCA 6 tabulate footing sizes for decks built exactly to their rules. Anything outside those rules needs an engineer or your building department's sign-off.
A narrow tube on its own has a small bearing area. Many builders put a wider footing under it (see the next section), which spreads the load without filling a large-diameter tube all the way up.
Bags or ready-mix for tube pours?
Tube pours are often done with bags because the volume per pier is small and the piers are spread around the site. Ten 12 in × 4 ft piers come to 1.22 yd³ (33 ft³), or 55 bags of 80 lb mix. That's a full day of mixing for two people. If the truck can reach most of the holes, a small ready-mix load poured straight from the chute is faster and gives you one consistent batch. Plants often charge extra for small loads, so get a delivered price before deciding.
Common mistakes
- Using the outside diameter. The tube wall is thin, so the error is small, but nominal sizes can differ from the true inside size. Measure it.
- Forgetting the part buried in the ground. Height means the full concrete height, from the bottom of the hole to the top of the tube, not just the part above grade.
- Letting tubes float or tip. Partly backfill before the pour and brace the top.
- Pouring onto loose soil. Tamp the hole bottom, or put the tube on a compacted footing, so the pier doesn't settle.
Checked against
Each case below is re-run against the calculator by our automated test suite.
| Case | Our result | Checked against | Result |
|---|---|---|---|
| One 12 in column, 4 ft tall, no waste: volume | 0.12 yd³ (3.1 ft³) | calculator.net concrete calculator | Match |
| Case | Our result | Checked against | Result |
|---|---|---|---|
| One 30.5 cm column, 1.22 m tall, no waste: volume | 0.089 m³ (89 L) | calculator.net concrete calculator | Match |
Frequently asked questions
How many bags for a 12 in × 4 ft Sonotube?
About 3.14 ft³, which works out to 6 bags of 80 lb mix (3.14 ÷ 0.60 = 5.2, rounded up) before waste.
How much concrete in a 10 in tube per foot?
About 0.55 ft³ per foot of height.
How many bags for an 8 in Sonotube?
About 0.35 ft³ per foot. A 4 ft tube takes about 1.4 ft³, or 3 bags of 80 lb mix.
Can I use this for a round slab?
Yes. Enter the slab diameter and its thickness in feet as the height (4 in = 0.333 ft).
Sources & assumptions
The results are planning estimates, and the cost figures only use prices you enter. Product yields, densities and coverage rates vary, so check the label or ask your supplier, and follow local codes. Figures marked "approximate" or "rule of thumb" are general practice, not exact standards.
See how we calculate and test our formulas and the changelog. Last updated 2026-10-08.
Reviewed by the MaterialWhiz Editorial Team. This estimate uses the assumptions shown in the calculator. Review the result against your supplier's product coverage and site conditions. Last reviewed: October 10, 2026. See how we calculate · Report a correction.