Calculators · Sonotube Calculator

Concrete & masonry

Sonotube Calculator

Pick the tube diameter and type the height to get the cubic yards of concrete and the number of 40, 60 and 80 lb bags.

Tube diameter

Sizes are nominal. If it matters, measure the inside of your tube.

Height of concrete in each tube

Number of tubes

Empty counts as 1.

Pad under each tube

Optional. Adds the concrete of a pad poured below the tube.

Waste to add (%)

Optional. Empty counts as 0%.

How to calculate the concrete for a Sonotube

A Sonotube is a round column, so the concrete is the volume of a cylinder. Take the radius, which is half the diameter, square it, multiply by π and by the height, all in feet. Then divide by 27 to get cubic yards. Type the diameter in inches and the calculator turns it into feet for you.

Step	Formula
1. Cubic feet per tube	π × (diameter in feet ÷ 2)² × height in feet
2. Cubic yards	cubic feet × number of tubes ÷ 27
3. Bags	cubic feet × number of tubes ÷ yield of the bag, rounded up

Example: four 12 inch tubes, 4 feet of concrete each

You set four 12 inch tubes and fill each one 4 feet deep. You add 10% waste. These are the figures the calculator gives when you type them in.

Step	Operation	Result
One tube	π × 0.5² × 4	3.1416 ft³
Four tubes	3.1416 × 4	12.57 ft³
With 10% waste	12.57 × 1.10	13.82 ft³
Cubic yards	13.82 ÷ 27	0.5120 yd³
80 lb bags	13.82 ÷ 0.60 = 23.04, rounded up	24 bags
60 lb bags	13.82 ÷ 0.45 = 30.72, rounded up	31 bags
40 lb bags	13.82 ÷ 0.30 = 46.08, rounded up	47 bags

Concrete for each Sonotube size

This table is for one tube filled to 4 feet and has no waste. The bag counts use the QUIKRETE Concrete Mix yields of 0.60 cubic feet for an 80 lb bag and 0.45 for a 60 lb bag (data sheet revised October 2022, checked October 2026) and are rounded up.

Tube diameter	ft³ per foot	yd³ per foot	80 lb bags for 4 ft	60 lb bags for 4 ft
6 in	0.196	0.0073	2	2
8 in	0.349	0.0129	3	4
10 in	0.545	0.0202	4	5
12 in	0.785	0.0291	6	7
14 in	1.069	0.0396	8	10
16 in	1.396	0.0517	10	13
18 in	1.767	0.0654	12	16
20 in	2.182	0.0808	15	20
24 in	3.142	0.1164	21	28
30 in	4.909	0.1818	33	44
36 in	7.069	0.2618	48	63

Sonoco’s own bag chart for its Builder’s Tube (Sonoco web page, checked October 2026) gives the same 80 lb counts for 4 feet of height in its 8, 10, 12 and 16 inch sizes, which are 3, 4, 6 and 10 bags. For 60 lb bags it gives the same counts for 8, 10 and 16 inches. For 12 inches it says 8 bags where the math gives 7. QUIKRETE’s table for its QUIK-tube agrees with 7 bags of 60 lb. The calculator counts the yield, not a chart, so you can always check it by hand.

Which Sonotube do you have?

Sonotube is Sonoco’s brand of fiber concrete forms. These are the lines and sizes in Sonoco’s brochures (Builder’s Tube, Round, a copy of Sonoco’s brochure kept by a distributor, and Commercial, checked October 2026):

Line	Diameters	Standard lengths	Use
Builder’s Tube	6, 8, 10 and 12 in	4, 8 and 12 ft	Decks, fences, posts. Below ground, up to 3 ft above the ground line
Round	6 to 36 in	12 ft	Footings, columns, sign, light pole and fence-post bases
Commercial	6 to 60 in	12 and 20 ft	Columns for commercial buildings, bridges, parking decks and stadiums

Sonoco’s brochure says the diameter sizes are nominal and that you need to measure if it is critical. It also says Builder’s Tube should not be used with mechanical vibrators and should be dry before it is filled. The Round and Commercial brochures say that concrete must be vibrated during the pour, so follow the brochure of the line you use.

Pad, gravel and the hole around the tube

Pad under the tube. If your design has a pad, choose “Round pad” or “Square pad” and type its size and thickness. Its concrete is added for every tube.
The hole. For its QUIK-tube, QUIKRETE says to dig a hole twice the diameter of the tube and, for footings, to put about 2 inches of gravel in the bottom and pour a 4 to 6 inch footing before setting the tube. That is QUIKRETE’s instruction for its own tube. Your plans decide what your job needs.
Above ground. Sonoco says that Builder’s Tube needs a collar or a wooden frame and side braces when it extends more than 2 feet above the ground line.
Other round holes. For a fence or deck post inside a hole, use the post hole concrete calculator, which subtracts the post. For several kinds of footings at once, use the concrete footing calculator.

Frequently asked questions

How much concrete does it take to fill a 12 inch by 4 foot Sonotube?

A 12 inch tube holds π × 0.5² = 0.7854 cubic feet per foot of height, so 4 feet is 3.14 cubic feet, which is 0.116 cubic yards. With the QUIKRETE Concrete Mix yields that is 6 bags of 80 lb or 7 bags of 60 lb, rounded up.

How many bags of concrete do I need for a Sonotube?

It depends on the diameter and the height. Multiply the cubic feet of your tube by the number of tubes and divide by the yield of the bag, which is 0.60 cubic feet for an 80 lb bag and 0.45 for a 60 lb bag. For 4 feet of height, the 80 lb bags per tube are 2 for a 6 inch tube, 3 for 8 inches, 4 for 10 inches, 6 for 12 inches and 10 for 16 inches. The table above lists more sizes.

Can I use a 6x6 post on a 10 inch Sonotube?

A square post must fit across its diagonal, which is its width times 1.414. A 10 inch tube has room for a square post up to 7.07 inches wide. A post that measures 5.5 inches across has a diagonal of 7.78 inches, so it fits. We did not find an open source for the real size of a 6x6, so measure your post. Tube diameters are also nominal, so measure the inside of your tube too.

How high above the ground can a Sonotube stand?

Your plans and building code decide the height of a pier. For the tube itself, Sonoco says its Builder’s Tube is designed for below ground placement but can be used up to 3 feet above the ground line, with a collar or a wooden frame and side braces if it extends more than 2 feet above it.

What diameters does a Sonotube come in?

Sonoco lists Builder’s Tube in 6, 8, 10 and 12 inch diameters, its Round forms from 6 to 36 inches and its Commercial forms from 6 to 60 inches. The calculator’s menu has the sizes in Sonoco’s concrete table, from 6 to 36 inches in steps of 2. For another size, choose “Other size” and type the diameter.

Should I add extra concrete for waste?

It depends on the job and the supplier. Cemex suggests adding 10 to 15% to a ready-mix order, and Sakrete suggests adding 10% to every estimate. Type the percentage in the waste box and the calculator adds it for you.

Do I need a pad or gravel under the tube?

That depends on your plans and code. For its own QUIK-tube, QUIKRETE says to place about 2 inches of gravel in the bottom of the hole, drive a rebar into the center and pour a 4 to 6 inch footing before setting the tube. If your design has a pad under each tube, choose its shape in the calculator and its volume is added.

This page does not show prices, because they change by region and supplier. Take the cubic yards and the bag counts to your supplier and ask for a quote. For other shapes and the full list of bag sizes, see the concrete calculator.