Concrete Estimator – Tube

The concrete in a round tube form is its volume: pi times the radius squared times the height, where the radius is half the diameter. Work in feet, so a 12-inch tube is 0.5 ft radius, and a 4-foot-tall pour is pi times 0.5 squared times 4, which is about 3.14 cubic feet, or 0.12 cubic yards.

Multiply by the number of tubes, then add a waste allowance of about 10 percent for spillage and oversized holes. Divide cubic feet by 27 to get cubic yards.

If there is a footing under each tube — a square pad or a flared bell — add its volume too. For bagged concrete, divide the total cubic feet by the bag’s yield to get the number of bags.

Divide the total volume you need by the yield of one bag and round up. An 80 lb bag of premixed concrete yields about 0.60 cubic foot, a 60 lb bag about 0.45, a 50 lb fast-setting bag about 0.375, and a 40 lb bag about 0.30 cubic foot.

For example, a single 12-inch tube 4 feet tall holds about 3.14 cubic feet, which is roughly 6 bags of 80 lb concrete once you round up and add a little waste.

Tube forms add up fast with height and diameter, so for several large piers it is worth comparing bagged concrete against a ready-mix truck, which is usually cheaper per yard for larger volumes.

Sonotube is a well-known brand of cardboard tube form used to cast round concrete columns and piers. The term is often used generically for any cardboard tube form. You set the tube in a hole or above grade, pour concrete into it, and peel away the cardboard once it cures.

They are used for deck and porch piers, fence and mailbox posts, structural columns, pole barn footings and anything that needs a clean round concrete pillar. Common diameters run from 6 to 12 inches for residential piers and larger for structural columns.

For deck and other structural piers, the tube usually sits on a wider footing — a poured pad or a flared bell form — and extends below the frost line so the pier does not heave.

Concrete piers generally must extend below the local frost line so that freezing and thawing of the ground does not push them up and heave whatever they support. Frost depth varies widely — from a few inches in warm climates to 48 inches or more in cold northern regions — and your building department sets the required depth.

On top of reaching frost depth, the pier and its footing have to be sized for the load they carry and the soil’s bearing capacity, which is why decks and structural columns are engineered rather than guessed.

This calculator works out the concrete volume for the tube height and footing you enter; it does not determine how deep or how wide they need to be, so confirm both with your local code.

Usually yes. Most codes require a wider footing under a pier so the load is spread over enough soil to prevent settling. The two common options are a square poured pad beneath the tube, or a flared bell-shaped footing form such as a Bigfoot that the tube plugs into.

The footing is typically about twice the tube diameter, and its size depends on the load and the soil’s bearing capacity. A bell footing is convenient because it combines the footing and the base of the pier in one pour.

This calculator lets you add either a square pad or a bell footing under every tube and includes its concrete in the total. Confirm the required footing size with your engineer or building department.

It depends on the total volume. For a few small piers, bagged premix concrete is simplest and usually cheapest once you factor in the delivery minimum and short-load fees that come with ready-mix.

As the number and size of the piers grows, the math flips: mixing dozens of bags by hand is slow and labor-intensive, and a ready-mix truck becomes cheaper per cubic yard and far faster to place. Most plants have a one-yard minimum, so very small orders pay a premium for delivery.

Compare the all-in cost — bags plus your time, or ready-mix plus delivery and short-load fees — for your specific volume. This calculator shows both, including the cost of the tube forms, so you can see the crossover.

A bell or flared footing is shaped like a truncated cone (a cone with the point cut off), widening from the tube diameter at the top to a larger base diameter at the bottom. Its volume uses the cone-frustum formula: pi times the height, divided by 3, times the sum of the top radius squared, the bottom radius squared, and the top radius times the bottom radius.

In practice you enter the base diameter, the tube diameter and the height of the flared section, and the calculator works out the frustum volume and adds it to the straight tube above.

Manufactured bell forms publish their concrete volume for each size, so for a specific product you can also just use its stated figure. Either way, add the bell volume to the tube volume for the total per pier.

Normal-weight concrete weighs about 145 pounds per cubic foot, or roughly 3,900 to 4,000 pounds per cubic yard. That is why even a modest set of piers adds up to a surprising amount of weight.

For example, a single 12-inch tube 4 feet tall holds about 3.14 cubic feet, which weighs around 455 pounds of concrete. A dozen such piers is over 5,000 pounds of material to mix and place.

The weight matters for planning how you will move and pour the concrete, whether you need a mixer or a truck, and how much help you will want on site. Lightweight concrete mixes weigh less but are not typically used for structural piers.