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Sonotube Calculator

Construction

Calculate cubic yards of concrete needed to fill cylindrical sonotube forms for deck footings and posts. Enter diameter, height, and quantity for instant total.

Reviewed by the thecalcu.com team · Last updated July 7, 2026

448
0.520
1

Concrete Needed

0.12
Total Volume
3.14

This calculator computes your Concrete Needed, Total Volume from the values you enter.

Inputs
Tube DiameterTube HeightNumber of Tubes
Outputs
Concrete NeededTotal Volume

What is a Sonotube?

A Sonotube Calculator figures out how much concrete you need to fill cylindrical cardboard forms, commonly known by the brand name Sonotube, used for round concrete footings and piers. These tubes are the standard method for pouring deck post footings, fence post bases, and column foundations below the frost line.

Because concrete is sold by the cubic yard (or by the bag for smaller jobs), getting the volume right before you order matters, too little and you're stuck with a partial pour, too much and you've paid for waste. This calculator uses the cylinder volume formula to convert your tube's diameter and height directly into cubic yards, so your ready-mix order or bag count is accurate the first time. It pairs well with the Sealant Calculator for sealing joints after the concrete cures, and the Cubic Yard Calculator for broader concrete volume estimates.

Why Use a Sonotube Calculator?

Ordering the wrong amount of concrete is expensive either way, a short pour means a return trip and a cold joint, while over-ordering ready-mix wastes money on unused material. If you're setting deck posts, fence posts, or a small structural footing, knowing the exact cubic yardage up front lets you order precisely what the job needs.

It's also essential for budgeting: multiply the total cubic yards by your local concrete price per yard to get an accurate materials cost for a bid, rather than a padded estimate. This is particularly useful alongside a Rebar Calculator when reinforcing footings.

Who Should Use This Calculator?

  • DIY homeowners setting deck or fence posts who need to know how many bags of concrete mix to buy.
  • Deck builders calculating footing volumes as part of a larger Decking Calculator project.
  • General contractors ordering ready-mix concrete for multiple footings on a job site.
  • Fence installers pouring post footings and wanting an accurate materials estimate before starting.
  • Structural and landscape contractors pouring column bases or light structural piers who need quick volume checks.

What Insights Does the Sonotube Calculator Give You?

Concrete Needed (in cubic yards) is the primary result, this is the number to use when ordering ready-mix concrete, since suppliers typically price and deliver by the cubic yard, often with a minimum order.

Total Volume (in cubic feet) is useful for smaller jobs where you're buying bagged concrete mix instead of ready-mix. Since most bags list their yield in cubic feet, this figure lets you divide directly to get a bag count without needing to convert units yourself.

How to use this Sonotube calculator

  1. Enter the Tube Diameter in inches, matching the size of sonotube form you're using.
  2. Set the Tube Height in feet, this should account for the required depth below the frost line plus any height above grade.
  3. Enter the Number of Tubes you're pouring for this project.
  4. Read the Concrete Needed result in cubic yards for ordering ready-mix.
  5. Cross-check with Total Volume in cubic feet if you're buying bagged concrete mix instead.
Show formula & methodology ↓Show less ↑

Formula & Methodology

The calculator treats each sonotube as a cylinder and applies the standard cylinder volume formula:

Volume per Tube (ft³) = π × (Diameter ÷ 24)² × Height

Total Volume (ft³) = Volume per Tube × Quantity

Cubic Yards = Total Volume ÷ 27

Worked example: For a 12 in diameter tube, 4 ft tall, with a quantity of 1: Radius = 12 ÷ 24 = 0.5 ft. Volume per Tube = π × 0.5² × 4 ≈ 3.14 ft³. Total Volume = 3.14 ft³. Cubic Yards = 3.14 ÷ 27 ≈ 0.12 yd³.

Frequently Asked Questions

How much concrete do I need for a sonotube footing?
The amount depends on the tube's diameter and height, a 12 in diameter tube that's 4 ft tall needs about 0.15 cubic yards of concrete, while a wider or taller tube needs proportionally more. The Sonotube Calculator computes this instantly from your diameter, height, and quantity so you can order the right amount of ready-mix or the right number of bags.
What is the formula for sonotube concrete volume?
Volume is calculated using the cylinder formula: π × radius² × height, where radius is half the tube's diameter converted to feet. Multiplying that per-tube volume by the number of tubes gives total cubic feet, which is then divided by 27 to convert to cubic yards, the standard unit concrete is sold in.
What is the difference between a sonotube and a regular concrete form?
A sonotube is a cylindrical cardboard or fiber form specifically designed for round concrete piers and footings, commonly used for deck posts, fence posts, and column bases. Unlike rectangular wood forms, sonotubes create a smooth round column and are typically removed or peeled away after the concrete cures.
How many bags of concrete do I need per sonotube?
An 80 lb bag of concrete mix yields about 0.6 cubic feet of concrete once mixed. Divide the calculator's Total Volume result (in cubic feet) by 0.6 to estimate the number of 80 lb bags needed, rounding up to avoid running short mid-pour.
Why does sonotube diameter matter so much for concrete volume?
Concrete volume scales with the square of the radius, so doubling the diameter of a sonotube roughly quadruples the amount of concrete needed for the same height. Even a small increase from a 10 in to a 12 in tube noticeably increases the required volume, which is why getting the diameter right before ordering concrete matters.
How do I use the Sonotube Calculator?
Enter the tube's Diameter in inches, the Tube Height in feet, and the Number of Tubes you're pouring. The calculator returns the total concrete needed in cubic yards along with the total volume in cubic feet for cross-checking against bag counts.
Can I calculate multiple sonotubes of different sizes at once?
This calculator handles multiple tubes of the same diameter and height using the Quantity field. If your project uses tubes of different sizes, run the calculation separately for each size group and add the resulting cubic yard totals together.
How deep should sonotube footings be for deck posts?
Frost-line depth requirements vary by region and local building code, typically ranging from 12 in in warm climates to 48 in or more in cold-winter regions. Check your local building department's frost depth requirement before setting the Tube Height, since footings poured above the frost line can heave over winter.
Should I order extra concrete beyond the calculated amount?
Yes, most contractors add a 5-10% buffer to account for form imperfections, minor spillage, and ground irregularities at the base of the tube. For small residential jobs with just a few footings, rounding up to the next full bag or half-yard of ready-mix is a common practical approach.
What sizes do sonotubes typically come in?
Sonotubes are commonly sold in diameters from 6 in up to 36 in or larger, with 8 in, 10 in, and 12 in being the most typical sizes for residential deck and fence post footings. Larger diameters are generally used for structural columns or heavier load-bearing applications.
Also known as
sonotube concrete calculatorconcrete footing calculatorround form concrete calculatordeck footing concrete calculatorcylindrical concrete form calculator