Calculating Tube ID

Here, we are going to introduce you to information surrounding the process of ‘Calculating Tube ID’. Why would you need to know something like this? Tube ID is necessary for us – at Torq N’ Seal Plugs – to provide customers with the correct TNS plugs. To help you figure out tube measurement, this will serve as a type of reference guide. With it, you won’t have to make tube measurements physically to figure out tube ID and correct TNS plugs. You can also reference our Tube Gauge chart.

What You Will Need

In order to calculate tube ID, you’re going to need the following information:

  • Tube outside diameter
  • Wall thickness

The calculation you will use is as follows: ID equals OD minus 2 times WT

For example: 0.750” minus (2 times 0.120”) equals 0.510”

The graphic above provides a visual reference for the calculation:

With that out of the way, let’s talk about tube leaks and why tube ID is important.


ID & Wall

Calculator to get ID from OD and Wall of stainless steel tube

Calculator to get Wall from OD and ID of stainless steel tube

NOTE: Please use format X.XXX for all dimensions. For example, 0.750 to represent 3/4″ or 0.875 to represent 7/8” or 1.250 to represent 1 1/4”

Leaks in Tubes

For any number of reasons, tube leaks can occur. The formation of holes remains the most common cause. Tube holes can form as a result of improper cleaning heads, corrosion, deposit buildup, etc. Tube leaks can also be the result of incomplete expansions and joint failures. Throughout all industries, tube plugging is a common necessity as a result. There are various types of plugs that can be used depending on the application, industry, and more. There are mechanical plugs, two-piece plugs, and one-piece plugs.

Tube Plugs

Whenever possible, you should match the material of the plug to the material of the tube. Why is this? It has everything to do with galvanic reactions. Here’s a simplified explanation of galvanic reaction/corrosion: When two different alloys or metals are regularly connected by moisture or immersed in a corrosive solution, each can develop the potential for corrosion. If conditions for corrosion are present:

  • The part of the cathode is played by the more noble metal.
  • The role of the anode is played by the more active metal.

What does that mean for you? It means, as just stated, the material of the tube and plug should match, if at all possible. However, if you must choose a different material for plugging, follow this rule of thumb: In a less noble tube material application, use a more noble plug material. This has everything to do with the relative surface area effect, eliminating concerns of galvanic reaction.

Choosing Your Plug

All in all, to make sure you have the plug that’s right for the job, you must consider the following:

  • Tube ID
  • Material
  • Application

As an example, you will likely choose a one-piece plug if you need to weld the plug in a low-pressure vessel. You may prefer a larger sealing area, however, if welding isn’t required, so a two-piece plug will probably work better. To achieve the best seal in a high-pressure, medium, and low-pressure situation, consider using a mechanical tube plug.

For Those Who Need Assistance…

A lot of information was documented above. It’s okay if you still have questions. We would be more than happy to answer them for you.

Please contact Torq N’ Seal Plugs at 201-641-2130 for information or a quote.

You can also email us at

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