How to use the Sonotube calculator
- Enter the tube. Type the inside diameter of the tube and the height you will fill with concrete. Use a quick diameter button for an 8, 10 or 12 inch tube.
- Enter the number of tubes. Type how many tubes of this size you will pour, and change the waste allowance and the bag size if you need to.
- Read the bags and the volume. The result shows the bags to buy in the chosen size, the bags in the other sizes, the cubic yards and the weight of the concrete.
What is a Sonotube calculator?
A Sonotube calculator is a tool that finds how much concrete fills a round form tube. A form tube is a cardboard cylinder that is set in the ground or on a footing and filled with concrete to make a round pier or column. Sonotube is a registered trademark of Sonoco, as Sonoco's own brochure for its concrete forms states, and many people use the name for any round concrete form.
The calculator treats the tube as a cylinder. It gives the answer in bags first, because small piers are usually poured from bags, and in cubic yards for larger jobs.
Features
- Bags of concrete for a tube of any diameter and height
- Quick buttons for 8 inch, 10 inch and 12 inch tubes
- Any number of tubes of the same size in one result
- Bag counts for 40 lb, 50 lb, 60 lb and 80 lb bags
- Volume in cubic yards, cubic feet and cubic metres, and the weight of the concrete
- A cost from your own price per bag or per cubic yard
- A live 3D preview, a PDF of the estimate and a WhatsApp share button
What you can use it for
- Piers for a deck, a porch or a carport
- Footings for a pergola, a pole barn or a sign
- Round concrete columns above the ground
- Comparing tube sizes before you buy
How the concrete in a tube is calculated
Volume = π × (diameter ÷ 2)² × height, with the diameter and the height in feet. The answer is in cubic feet.
Worked example: a 12 inch tube, 4 feet tall
- Radius: 12 in ÷ 2 = 6 in = 0.5 ft.
- Volume: 3.1416 × 0.5² × 4 = 3.14 cubic feet, which is 0.116 cubic yards.
- With 10% waste: 3.46 cubic feet.
- 80 lb bags at 0.60 cubic feet each: 3.46 ÷ 0.60 = 5.8, so 6 bags.
These are the numbers the calculator shows when the page opens.
Concrete per foot of tube, by diameter
The table is plain geometry. The bags column is for a tube filled 4 feet high with 80 lb bags and no waste, rounded up to a full bag. The diameters are examples: use the inside diameter of your own tube.
| Inside diameter | Cubic feet per foot of height | 80 lb bags for 4 ft |
|---|---|---|
| 6 in | 0.196 | 2 |
| 8 in | 0.349 | 3 |
| 10 in | 0.545 | 4 |
| 12 in | 0.785 | 6 |
| 14 in | 1.069 | 8 |
| 16 in | 1.396 | 10 |
| 18 in | 1.767 | 12 |
| 24 in | 3.142 | 21 |
Bag yields are from the Quikrete Concrete Mix data sheet (product 1101, revised October 2022): an 80 lb bag yields 0.60 cubic feet.
What the calculator includes
- The calculator counts only the concrete inside the tube. A footing under the tube is a separate pour: add it with the concrete calculator.
- The steel inside the tube is ignored, so the real volume of concrete is slightly lower.
- Use the inside diameter. If you are not sure of it, measure the tube.
- Each dimension can be up to 10,000 in its unit, the number of tubes up to 1,000 and waste 0 to 50%.
- This site is not affiliated with Sonoco, the owner of the Sonotube name.
Is it private?
Yes. The calculation and the PDF are made in your browser. The numbers you type are not sent to our server and are not saved.
Tips for an accurate estimate
- Measure the inside diameter of the tube you will buy; the label size is the form size.
- Measure the depth from the bottom of the hole to the top of the form, including any part above ground.
- If the hole is wider than the tube at the bottom, add that part as a separate cylinder.
- Set and brace the tubes plumb before you count the bags, so you know the final height.
- Mix enough bags for one tube at a time to avoid a cold joint inside a pier.
Related calculators
Frequently asked questions
- How much concrete do I need for a Sonotube?
- Multiply π by the square of the radius in feet and by the height in feet. A 12 inch tube that is 4 feet tall holds 3.14 cubic feet of concrete, which is 6 bags of 80 lb mix with 10% waste.
- How many bags of concrete fill a 12 inch Sonotube?
- A 12 inch tube holds 0.785 cubic feet for each foot of height. With 80 lb bags that yield 0.60 cubic feet, that is about 1.3 bags per foot, so a 4 foot tube needs 6 bags.
- How many bags of concrete fill an 8 inch Sonotube?
- An 8 inch tube holds 0.349 cubic feet for each foot of height. A 4 foot tube holds 1.40 cubic feet, which is 3 bags of 80 lb mix.
- How many bags of concrete fill a 10 inch Sonotube?
- A 10 inch tube holds 0.545 cubic feet for each foot of height. A 4 foot tube holds 2.18 cubic feet, which is 4 bags of 80 lb mix.
- Does the calculator include the footing under the tube?
- No. It counts only the concrete inside the tube. Calculate the footing as a slab, a round pad or a footing in the concrete calculator and add the two results.
- Is this an official Sonotube tool?
- No. Sonotube is a registered trademark of Sonoco. This is an independent calculator that works for any round concrete form tube.
Sources
Every figure this calculator uses comes from the published sources below. The formulas are on this page, so any result can be checked by hand.
- Quikrete, Concrete Mix No. 1101: data sheet and product page. Bag yields: 0.30 ft³ (40 lb), 0.375 ft³ (50 lb), 0.45 ft³ (60 lb) and 0.60 ft³ (80 lb); bags per pallet: 80, 56 and 42.
- Federal Highway Administration (FHWA), Report FHWA-HRT-05-057. Normal-weight concrete: 145 lb per cubic foot (1.96 tons per cubic yard).
- Sonoco, Sonotube concrete forms brochure. Sonotube is a registered trademark of Sonoco.