Tubes are used for pouring concrete to help force the concrete to solidify in the desired shape, similar to the way a mold would be used. The tubes are strong enough to hold the concrete while it dries but also easy to tear away. Some concrete tubes have plastic liners on the inside that will remain after the tube has been taken away for a glossy finish. To calculate the amount of concrete you will need to fill the tube, you need to find the interior diameter and the height of the tube.

Measure the interior diameter of the round tube from the inside edge of the tube through the center to the inside edge on the other side.

Divide the interior diameter by 2 to find the radius. For example, if the interior diameter is 4 feet, the interior radius would be 2 feet.

Measure the height of the round tube. Use the same units as you did to find the interior diameter. For example, if you used feet for the interior diameter, measure the height in feet.

Determine the amount of concrete in the round tube by calculating the interior volume with the following formula where R is the interior radius, H is the height, ? is pi which can be approximated as 3.14, \"*\" means multiplication and \"^\" means raised to the power of: Volume = ? * R^2 * H For example, if the interior radius is 2 feet and the height is 10 feet, the volume of concrete would be about 125.6 cubic feet.

#### Things You Will Need

- Measuring tape