Sonotube Calculator

How to use the Sonotube concrete calculator

What this calculator does

This tool estimates the concrete needed to fill one or more cylindrical form tubes. It calculates the geometric volume of each cylinder, multiplies it by the number of columns, adds a user-selected waste allowance, converts the result to cubic feet and cubic yards, estimates wet concrete weight from density, and rounds premixed bags up to the next whole bag. It is a material-planning estimate, not a structural design tool. The correct footing diameter, reinforcement, embedment depth, bearing requirements, and concrete strength should come from approved plans or a qualified professional.

When to use it

Use the calculator when planning deck piers, porch supports, fence or gate posts, light-duty sign or lamp posts, and round architectural columns. It is also useful for comparing ready-mix volume with bagged-concrete quantities before deciding how to purchase material. Sonoco's overview of Sonotube concrete forms and product families explains the kinds of cylindrical forming products available.

How to calculate

1. The calculator opens with a complete demonstration: 16-inch diameter forms, 10-foot columns, six columns, 145 lb/ft³ concrete, 80-pound bags, and 8% waste. The results and Excel workbook are ready immediately.
2. Replace each demonstration value with the dimensions and quantity from your project. Use decimal points for fractional values; commas are not accepted as decimal separators.
3. Read “Concrete to order, including waste” as the purchasing volume. Review the supporting volume, weight, and bag outputs before ordering.
4. Select the bag size printed on the product you intend to buy. The bag result changes because it divides estimated wet weight by that bag weight.
5. Choose Download Excel to create a current-state workbook. Reset clears the demonstration and all calculated values; Download Excel then remains unavailable until a complete valid project is entered again.

Input guide

Sonotube diameter is required and accepts a positive inside diameter from 1 to 120 inches; 16 inches is a realistic example. A larger diameter increases volume with the square of the diameter, so a modest diameter change can materially change the order. Do not enter circumference or outside diameter. Column height is required in feet from 0.1 to 100; include any portion below grade. A 10-foot example means the entire filled length, not only the visible portion. Volume changes directly with height.

Number of columns is a required whole number from 1 to 10,000. Six means six identical cylinders; use separate calculations when column dimensions differ. Concrete density is required in pounds per cubic foot from 50 to 250. The 145 lb/ft³ demonstration is typical of normal-weight fresh concrete; density affects weight and bag count but not geometric volume. NRMCA's guidance on concrete yield and fresh density describes why weight and measured volume are linked.

Premixed bag size is required and uses a fixed list of common bag weights. Choose the package's net weight, not its stated nominal yield. Waste allowance is required from 0% to 50%; 8% is a practical planning example. It adds material for spillage, over-excavation, irregular bottoms, and handling. Do not use waste allowance to compensate for an incorrectly measured diameter or height.

Output guide

Concrete to order, including waste is the primary estimate in cubic yards. Net concrete volume excludes waste, while Volume per column shows one cylinder. Wet concrete weight uses the selected density and includes waste. Premixed bags needed divides that weight by the selected bag size and always rounds upward. The summary pills repeat diameter, quantity, and waste so the assumptions stay visible. In the table, “Per column” is one form, “All columns” excludes waste, and “With waste” includes the allowance. Zero waste makes the last two columns equal; high waste should be justified by site conditions rather than used automatically.

Worked example

For the opening example, a 16-inch diameter equals 1.3333 feet. The radius is 0.6667 feet, so one 10-foot cylinder contains π × 0.6667² × 10 = about 13.40 cubic feet, or 0.517 cubic yard. Six columns require about 80.42 cubic feet, equal to 3.103 cubic yards. Adding 8% gives about 86.85 cubic feet, or 3.350 cubic yards to order. At 145 lb/ft³, the estimated wet weight is about 12,594 pounds; dividing by 80 pounds per bag and rounding up gives 158 bags. The exact on-screen and workbook values are generated from the same unrounded model.