Sonotube Calculator

Calculate the exact amount of concrete needed to fill cylindrical concrete forming tubes (Sonotubes) for deck footings, fence posts, and piers.

Number of tubes qty Please enter a positive quantity

Tube diameter inches Standard sizes: 8", 10", 12" Please enter a valid diameter

Tube depth (height) feet Depth to the bottom of the hole Please enter a valid depth

Concrete bag size

Select your preferred pre-mix bag weight

Waste buffer %

Accounts for spills and uneven bell-shaped bottoms Please enter a valid percentage

Calculation Results

Concrete required

— bags

Includes the requested waste buffer.

How to use this concrete tube calculator

Enter your pier dimensions

Input the number of tubes you are filling, the inside diameter of the tubes in inches, and the total depth/height of the hole in feet.

Select your bag size

Choose the weight of the pre-mixed concrete bags you plan to buy (50lb, 60lb, or 80lb). Standard structural concrete (like Quikrete 5000) typically comes in 80 lb bags.

Set a waste buffer

Leave the 10% waste buffer intact. When digging footings, the bottom of the hole is rarely perfectly flat, and standard practice often requires "belling out" the bottom for frost heave protection, which eats up extra concrete.

Review the material list

The tool outputs the exact number of bags needed, alongside the total volume in cubic yards in case you decide to order ready-mix delivery instead.

Sonotube Concrete Volume & Bag Requirements (80lb)

Tube Diameter	Hole Depth	Cubic Yards	80lb Bags Needed
6 inches	2 ft	0.015 yd³	1 Bags
6 inches	3 ft	0.022 yd³	1 Bags
6 inches	4 ft	0.029 yd³	2 Bags
6 inches	5 ft	0.036 yd³	2 Bags
6 inches	6 ft	0.044 yd³	2 Bags
6 inches	8 ft	0.058 yd³	3 Bags
6 inches	10 ft	0.073 yd³	4 Bags
8 inches	2 ft	0.026 yd³	2 Bags
8 inches	3 ft	0.039 yd³	2 Bags
8 inches	4 ft	0.052 yd³	3 Bags
8 inches	5 ft	0.065 yd³	3 Bags
8 inches	6 ft	0.078 yd³	4 Bags
8 inches	8 ft	0.103 yd³	5 Bags
8 inches	10 ft	0.129 yd³	6 Bags
10 inches	2 ft	0.040 yd³	2 Bags
10 inches	3 ft	0.061 yd³	3 Bags
10 inches	4 ft	0.081 yd³	4 Bags
10 inches	5 ft	0.101 yd³	5 Bags
10 inches	6 ft	0.121 yd³	6 Bags
10 inches	8 ft	0.162 yd³	8 Bags
10 inches	10 ft	0.202 yd³	10 Bags
12 inches	2 ft	0.058 yd³	3 Bags
12 inches	3 ft	0.087 yd³	4 Bags
12 inches	4 ft	0.116 yd³	6 Bags
12 inches	5 ft	0.145 yd³	7 Bags
12 inches	6 ft	0.175 yd³	8 Bags
12 inches	8 ft	0.233 yd³	11 Bags
12 inches	10 ft	0.291 yd³	14 Bags
14 inches	2 ft	0.079 yd³	4 Bags
14 inches	3 ft	0.119 yd³	6 Bags
14 inches	4 ft	0.158 yd³	8 Bags
14 inches	5 ft	0.198 yd³	9 Bags
14 inches	6 ft	0.238 yd³	11 Bags
14 inches	8 ft	0.317 yd³	15 Bags
14 inches	10 ft	0.396 yd³	18 Bags
16 inches	2 ft	0.103 yd³	5 Bags
16 inches	3 ft	0.155 yd³	7 Bags
16 inches	4 ft	0.207 yd³	10 Bags
16 inches	5 ft	0.259 yd³	12 Bags
16 inches	6 ft	0.310 yd³	14 Bags
16 inches	8 ft	0.414 yd³	19 Bags
16 inches	10 ft	0.517 yd³	24 Bags
18 inches	2 ft	0.131 yd³	6 Bags
18 inches	3 ft	0.196 yd³	9 Bags
18 inches	4 ft	0.262 yd³	12 Bags
18 inches	5 ft	0.327 yd³	15 Bags
18 inches	6 ft	0.393 yd³	18 Bags
18 inches	8 ft	0.524 yd³	24 Bags
18 inches	10 ft	0.654 yd³	30 Bags
24 inches	2 ft	0.233 yd³	11 Bags
24 inches	3 ft	0.349 yd³	16 Bags
24 inches	4 ft	0.465 yd³	21 Bags
24 inches	5 ft	0.582 yd³	27 Bags
24 inches	6 ft	0.698 yd³	32 Bags
24 inches	8 ft	0.931 yd³	42 Bags
24 inches	10 ft	1.164 yd³	53 Bags

Frequently asked questions

How much concrete do I need for a 12-inch Sonotube?

For a 12-inch diameter Sonotube that is 4 feet deep, you need approximately 3.14 cubic feet of concrete per tube. Using standard 80-pound bags (which yield about 0.60 cubic feet each), you will need roughly 6 bags per tube, including a small waste buffer.

Should I use bags or order ready-mix concrete?

If your total project volume is less than 1 cubic yard (about forty-five 80lb bags), mixing bags by hand or with a rented mixer is usually the most cost-effective route. If your project exceeds 1.5 to 2 cubic yards, ordering a ready-mix truck delivery will save you immense manual labor and ensure a consistent pour.

How deep do Sonotubes need to be?

The depth of your concrete piers must extend below your local frost line to prevent the ground from heaving and destroying your structure in the winter. In warm climates, this might be 12 inches; in northern climates, it can be 48 inches or deeper. Always check your local building codes.

Why do I need to add a waste factor?

A 10% waste buffer is critical when pouring concrete piers because real-world holes are never perfect cylinders. Digging often creates wider bases, rocks fall out of the sidewalls, and concrete inevitably spills during mixing. Running short on a single tube ruins the monolithic integrity of the pour.

About this calculator

This Sonotube calculator helps carpenters, deck builders, and DIYers generate accurate concrete estimates for cylindrical footings. By determining the exact geometric volume of your forming tubes, the tool translates cubic feet directly into standard pre-mixed bag quantities.

The mathematical formulas used in this estimator rely on the volume of a cylinder:

Radius (ft) = (Diameter (in) ÷ 2) ÷ 12
Volume per Tube (cu ft) = π × Radius² × Depth (ft)

Total Volume = (Volume per Tube × Quantity) × (1 + (Waste % ÷ 100))
Cubic Yards = Total Volume (cu ft) ÷ 27

Bags Needed = Total Volume (cu ft) ÷ Bag Yield (cu ft)

Bag yields used in this tool: An 80 lb bag yields approximately 0.60 cubic feet. A 60 lb bag yields 0.45 cubic feet. A 50 lb bag yields 0.375 cubic feet. Note that actual yields can vary slightly based on the exact mix design and how much water you add.