Sonotube Calculator

Created by Kenneth Alambra
Reviewed by Steven Wooding
Last updated: May 19, 2022

This Sonotube® calculator, or concrete calculator for Sonotubes, will help you estimate how much concrete you will need to build cylindrical concrete columns and posts with the help of the readily available and innovative cylinder forms called Sonotubes. In this calculator, you will learn:

  • What a Sonotube is;
  • How to use this Sonotube calculator; and
  • How to calculate concrete for Sonotubes.

We'll also briefly discuss how to use Sonotube's Concrete Requirements Size Chart in determining how much concrete you need for any Sonotube size. If you're ready to start learning about Sonotubes, then keep on reading.

What is a Sonotube?

Sonotube® is a brand of cylindrical-shaped concrete forms manufactured by the company Sonoco. These concrete forms are made of multiple layers of quality spiral-wound fiber glued together by some top-secret heavy-duty adhesive. Sonotubes are strong and durable, and you can use them for many uses.

In terms of their applications, Sonotube products are perfect for constructing:

  • Perfectly round columns for both residential and commercial buildings;
  • Round posts for deck supports, light posts, fence post supports; or
  • For anything that you would need a cylindrical post.

You can easily strip off the Sonotubes before the poured concrete hardens completely. You can also leave the Sonotubes on the columns depending on your application. They come in different types and durability, but all Sonotubes are capable of withstanding high pressures from wet concrete.

You can visit Sonotube's website to learn more about their products.

"Sonotube" is a registered trademark of Sonoco Plastics, Inc., which develops and manufactures packaging and some industrial products.

How to use this Sonotube calculator

This concrete calculator for Sonotube is very intuitive and easy to use. Nevertheless, here are the steps on how to use this tool:

  1. Select the Sonotube size you want to use. This measurement is also the same as your target diameter for your concrete column.
  2. Enter your desired column total height. If part of your column will be under the ground, add the height of embedment to the height of your column's exposed part. This measurement is also the length of Sonotube you need for this column.
  3. Input the number or quantity of columns you need to cast.

After performing these first three steps, our tool will display how much concrete you need for your Sonotube column. You can stop right here if you plan to order ready-mix concrete for this project. If you prefer to order pre-mixed concrete bags or mix concrete yourself, go ahead and proceed to the next steps.

For pre-mixed concrete bags:

  1. Choose I'll get pre-mixed concrete bags from the Concrete mix selection.
  2. Enter the concrete density your plan specifies for your project. Upon doing so, our calculator will display the weight of your required volume of concrete.
  3. Input the pre-mixed concrete bag size that you prefer to order.
  4. Finally, enter the wastage percentage you expect to waste while mixing your concrete and pouring it into your Sonotubes.

Expect our calculator to display the number of pre-mixed concrete bags you will need after doing that last step.

On the other hand, if you specifically want to mix concrete yourself:

  1. Choose I'll mix my own concrete from the Concrete mix selection. Our calculator will then display some of the most common mix ratio options from which you can choose.
  2. Select the concrete mix ratio specified on your construction plan.
  3. Enter the total wastage percentage for your concrete materials.

Upon doing the last step in this option, our concrete calculator will display the cement, sand, and gravel volumes you need for our project. You can also go to the Advanced mode of our calculator to enter the cost for each material you need to find the total concrete cost for your project.

In the next section of this text, let us discuss how to manually calculate how much concrete you need for your Sonotube columns.

How to calculate concrete for Sonotubes

Let's say we want to construct six 10-feet (or 120-inches) high concrete columns using 16-inch Sonotube concrete forms. For this, we can use the formula for cylinder volume to determine how much concrete we'll need for a single column, as shown below:

Vcolumn=π×d2×h÷4=π×162×120÷4=24,127.43 in30.5171 cubic yards\small \begin{align*} V_\text{column} &= \pi\times d^2\times h\div 4\\ &= \pi\times 16^2\times 120\div 4\\ &= 24,127.43\ \text{in}^3\\ &≈ 0.5171\ \text{cubic yards}\\ \end{align*}

where:

  • VcolumnV_\text{column} – Concrete volume per column;
  • dd – Column diameter or Sonotube size; and
  • hh – Height of column.

To find the total concrete volume we'll need for all columns, we simply multiply the volume needed for each column by the number of columns. For our example:

Vtotal=Vcolumn×n=0.5171 cubic yards×63.103 cubic yards\small \begin{align*} V_\text{total} &= V_\text{column} \times n\\ &= 0.5171\ \text{cubic yards} \times 6\\ &≈ 3.103\ \text{cubic yards}\\ \end{align*}

where:

  • VtotalV_\text{total} – Total volume of concrete needed;
  • VcolumnV_\text{column} – Concrete volume per column; and
  • nn – Number of columns.

Don't forget to take into consideration that some material may get wasted during construction. It's a good practice to add an extra 5-10% of the total volume for this purpose.

🙋 Note that aside from the concrete materials and cost, you will also have to consider the material cost for reinforcing bars, any anchor bolts or any deck hardware needed, concrete form release agent, and the cost of Sonotubes. You may also need to allot a budget for some bracing material to keep your Sonotubes vertically plumb as you pour your concrete.

Quick reference chart

A quick and easy way to determine how much concrete you will need for a single column for any available Sonotube size is by using the Concrete Requirements Size Chart Sonotube provides on their website. Here is a copy of that chart for your reference:

Diameter (inches)

Volume in cubic yards for various column heights

3′

6′

8′

10′

12′

16′

20′

6

0.022

0.044

0.058

0.073

0.088

0.117

0.146

8

0.039

0.077

0.103

0.129

0.155

0.208

0.258

10

0.061

0.121

0.162

0.202

0.252

0.323

0.404

12

0.087

0.176

0.233

0.291

0.349

0.466

0.582

14

0.119

0.238

0.317

0.396

0.475

0.634

0.792

16

0.155

0.310

0.414

0.517

0.620

0.827

1.034

17

0.196

0.392

0.523

0.654

0.785

1.046

1.310

20

0.242

0.485

0.646

0.808

0.970

1.293

1.616

22

0.293

0.587

0.782

0.978

1.173

1.565

1.956

24

0.349

0.698

0.931

1.164

1.397

1.862

2.328

26

0.410

0.820

1.093

1.366

1.639

2.186

2.732

28

0.475

0.950

1.270

1.584

1.901

2.534

3.170

30

0.545

1.091

1.454

1.818

2.182

2.909

3.636

32

0.621

1.241

1.655

2.069

2.483

3.310

4.138

34

0.701

1.401

1.868

2.335

2.802

3.736

4.670

36

0.785

1.571

2.094

2.618

3.142

4.189

5.236

40

0.970

1.939

2.586

3.232

3.878

5.171

6.464

42

1.069

2.138

2.850

3.563

4.276

5.701

7.126

48

1.396

2.792

3.723

4.654

5.585

7.446

9.308

54

1.7867

3.534

4.712

5.890

7.069

9.424

11.780

60

2.181

4.363

5.817

7.272

8.727

11.634

14.544

By going through the row of our desired Sonotube size, we can stop at the column of our post's height to find the concrete volume we need in cubic yards. Isn't that easy and quick?

Of course, you will still have to use your calculator if you need more than one column or post to build. Or, you can use our Sonotube calculator for more convenience! 😊

FAQ

What is a Sonotube used for?

Sonotubes are concrete forms that we can use to create perfectly round concrete columns or posts. Instead of manually shaping round concrete columns or assembling formworks using materials such as plywood to build round columns, we can use Sonotubes to save time, money, and labor. Sonoco, the manufacturer of Sonotubes, also offers Sonovoid – concrete forms used to make cylindrical holes.

How do I cut a Sonotube?

To cut a Sonotube:

  1. Measure how long your Sonotube needs to be and mark the point where you should cut.
  2. If you are cutting with a handsaw or any hand-held cutting tool, wrap a wide paper with a clean straight edge around the Sonotube. This paper will act as a straight edge so you can draw a perfect circle around the tube.
  3. Carefully follow the line you drew around the tube as you saw.

What sizes do Sonotubes come in?

Sonotubes come in a variety of sizes, from 6" to 60" in diameter and from 4′ to 20′ in length. You can refer to this table for the different sizes for each type of Sonotube available:

Sonotube Concrete Form

Diameter range

Length range

Custom lengths available?

Sonotube Finish Free

12"-48"

12′-20′

yes

Sonotube Commercial

6"-60"

12′-20′

yes

Sonotube Round

6"-36"

12′

yes

Sonotube Builder's Tube

6"-12"

4′

no

How many bags of concrete do I need to fill an 8-inch Sonotube?

You will need around one 25-kg bag of pre-mixed concrete to fill a foot height of an 8-inch Sonotube if you use 150 lb/ft³ concrete. To arrive at that bag number:

  1. Find the volume of a 1′ high 8" diameter column:

    Volume = π × (8 in)² × 12" / 4 = 603.2 in³ ≈ 0.3491 ft³

  2. Calculate the equivalent weight of the column:

    Weight = 0.3491 ft³ × 150 lb/ft³ = 52.3599 lb ≈ 23.75 kg

  3. Determine how many bags you need:

    Bags = 23.75 kg / 25 kg = 0.95 bag ≈ 1 bag

How big of a Sonotube do I need?

The size of Sonotube you need depends on the structure your column needs to support. When constructing a building, refer to the round column diameters specified in your plans. Chances are, a structural engineer analyzed and approved your plans. For smaller DIY projects, choose a size that will ensure at least an inch of concrete cover around the material you are embedding into the concrete.

Kenneth Alambra
Sonotube® size
12" (30.48 cm)
Height
ft
Quantity
pieces
Volume
cu yd
Concrete materials needed
Concerete mix
I'll get pre-mixed concrete bags
Concrete density
lb/cu ft
Weight
lb
Bag size
lb
Waste
%
Bags needed
bags
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