Pipe vs Tube

Is it pipe or tube? What’s the difference?

To look at them, you would not see differences between steel pipe and round tube. They look the same. In conversation, pipe and tube are used interchangeably, but there are significant differences between pipe and tube. The differ in their intended use, shape and sizing.

In their most elemental forms, pipe is designed for the conveyance of a fluid or gas and tube is designed for structural applications. There are, of course, exceptions to this elemental description, but it mostly holds true.

The intended purpose of pipe and tube helps explain the way that the two materials are sized. Pipe sizes, originally, emphasized the importance of the Inside Diameter (ID) as engineers were concerned with the flow of fluid or gas. It was, and still is, important that each pipe, of the same size, has a uniform ID to result in a uniform rate of flow. There are four descriptors for pipe sizes: Nominal Pipe Size (NPS), Outside Diameter (OD), Schedule & Wall Thickness. This gets a little confusing. For pipe sizes 1/8” through 12”, the NPS is LOOSELY based on the ID of the pipe, but they are not the same. For sizes, 14” and up the NPS is equal to the OD of the pipe. Basically, NPS is an antiquated method used to standardize pipe sizes way back when. As the pipe industry evolved, sizes changed. Today, it is understood that NPS does not equal ID. OD is a more accurate descriptor of the dimension of pipe. Meaning, if you were to draw a measuring tape across the end of a piece of pipe the reading would be equal to the “OD”. So, OD = OD. Every schedule has a wall thickness, but not all wall thicknesses have a schedule. Schedule and wall thickness are used to define the wall of the pipe. How thick is the wall of the pipe? This is a little tricky, too. Pipes have schedules ranging from 5S to XXH (or XXS). This gets confusing because the actual wall thickness (inches or mm) changes based on the OD of the pipe. So, 2” Std pipe has a wall thickness of 0.154”, but 3” Std pipe has a wall thickness of 0.216”. So, schedule “standard” can have multiple wall thicknesses based on the pipe OD. There are pipe sizes that have a wall thickness greater than XXH, these are heavier than scheduled pipes.

Having said all of that, how is pipe ordered?

Well, it sort of depends on the buyer. The same order can be stated two different ways:


Option A:       2.000” XH Pipe (NPS x Schedule)

Option B:       2.375” x .218” Pipe   (OD x Wall Thickness)

Options A & B are equivalent.

Unlike tubing, steel pipe is exclusively round (cylindrical) and rigid.

Tubing can come in a range of shapes: round, square, rectangle, to name a few. The dimensional emphasis is on the OD of the tube and the wall thickness (sometimes called gauge). Because tubing is generally not used for the conveyance of a fluid or gas, the ID becomes less important. Tube applications require a more involved manufacturing process and tighter OD tolerances than pipe. As such, tube, on average is more expansive than pipe.

Tube sizes are actual sizes. Meaning a 2” outside diameter is really a 2” outside diameter. (Remember that 2” pipe really has an outside diameter of 2.375”).

Whether you are looking for pipe or tube Bryzos can help you source material. The Bryzos negotiating platform was designed to accommodate many sizes and shapes of steel goods. Pipe and tube are no problem.

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