How to Figure Concrete for Piping

Concrete is ideal for making large pipes.

Industrial manufacturers use metal and plastic to make durable pipes of small diameter, but for larger pipes, the cost of metal and plastic can be prohibitive. Concrete is both versatile and relatively inexpensive, which is why builders often use concrete to form bigger pipes. The volume of a concrete pipe is the difference in volume between two cylinders. You can apply the formula for cylindrical volume to figure the amount of concrete needed for piping.

Instructions

1. Call the outside radius of the pipe "R." For example, if you are going to construct a pipe that is five feet wide on the outside, R = 2.5, since the radius is half the diameter.

2. Call the inside radius of the pipe "P." For instance, if the inside diameter is four feet, P = 2.

3. Compute the quantity R^2 - P^2. Using the example above, if R = 2.5 and P = 2, then R^2 - P^2 = 6.25 - 4, which equals 2.25.

4. Multiply this number by the length of the pipe. For example, if the length is 12 feet, you compute (12)(2.25) = 27.

5. Multiply this number by pi, which is approximately equal to 3.1416. This gives you the volume of concrete. Using the example above, the volume of the pipe is 84.8232 cubic feet.

Tips & Warnings

• The volume of a cylinder with radius R and length L is pi(L)(R^2). The difference in volume of two cylinders with the same length and different radii is pi(L)(R^2 - P^2).

References

• Renton Technical College: Cylinder Volume Lesson Plan