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How to Measure Pipe Fittings: Understanding the Process

How to measure pipe fittings is important to understand. Read all about the process below.

How to Measure Pipe Fittings: Understanding the Process - KB Delta

One factor determining how successful a particular piping project is involves accurate measurements. If you do not know how to measure pipe fittings and pipe sizes accurately, your project has already failed.

This is why learning how to take accurate measurements of pipe fittings, etc., is crucial and must never be taken for granted.


Finding the Right Pipe Fittings

As mentioned earlier, how successful your project is has a lot to do with the accuracy of your measurements. When it comes to fittings and pipes, you need to always find the perfect or right size.

This can be somewhat confusing, especially if you need to gather supplies of accurate sizes for a specific project. No one wants to be halfway done with the project only to discover that more than a few pieces do not fit accurately together. This could be why most commercial piping projects take ample help from professional Plumbing services so that these little details are sorted out smoothly, leading to reduced expenditure in the long run. However, pipe measurements are something that can be learned with a little effort.

Learning how to take accurate measurements of fitting sizes and pipes is not straightforward, but it is not rocket science. The most important step to take in order to speedily learn how to measure pipes and fittings accurately is to find and use the right measuring equipment for your next project.


How to Measure Nominal Pipe Size

Several factors and measurements can help determine the nominal size of a pipe. This includes the circumference or outside diameter.

In order to obtain an accurate reading of the nominal pipe size, start by measuring the circumference and threads per inch. If you are dealing with a female pipe thread, you have to measure the inside diameter at the widest point of the threads. But for male pipe threads, ensure you measure the circumference at the widest point of the threads.

Use these measurements to discover the perfect/right size in a nominal pipe size conversion chart.


Actual Dimensions vs. Nominal Sizes

‘Pipe size’ is often the element that causes many people to make errors. In reality, pipe size has to do with the pipe’s nominal diameter or size. It is the nominal size plumbers use when describing or shopping for fittings and pipes.

For instance, tubing – such as the soft copper used in rolls – is generally measured by its outside diameter. The outside diameter of copper tubing is usually rounded to the nearest 1/8th of an inch for top-notch accuracy.

The misleading aspect is that the outside diameter measurement of tubing is not the nominal pipe size. This often creates highly perplexing or confusing plumbing issues when measuring pipe size accurately.

Taking the measurement of the pipe is not the same as measuring both the outer and inner diameters. The diameters of the pipe can change, depending primarily on the thickness of the material used in making the pipe. Moreover, the pressure rating of that pipe has zero significance.

For instance, 2 different -inch pipes may have varied outer and inner diameters since they have varying wall thickness. This is the primary reason why the nominal size of a pipe plays a crucial role in measuring fitting and pipe sizes.

Pipes with heavy pressure ratings and thick walls maintain the same outside diameter, which will remain the same. This ensures you get a snug and excellent fit right inside a socket.

But as the pipe wall changes, its inside diameter becomes smaller while the outside diameter remains the same. This is the same for inch/imperial sizes as well as metric sizes.

The inch/imperial and metric sizes are 2 unique systems. The inch/imperial system typically labels pipe diameters in inches, while the metric system usually labels pipe diameters in millimeters.


What Manufacturers Do

Some pipe manufacturers employ the same molds for their inch/imperial fittings as they do for their metric fittings. For instance, a Comer fitting comes with 2 numbers. If these numbers read ’80 – 4,’ the fitting is precisely 80mm and 4 inches.

However, you should know that it can’t be both since these are different measurements. Since the manufacturers use the same mold, they do not change the stamp on the fittings.

For the ‘90 – 3′ example, you may need to measure the outside diameter in order to figure out whether it was a 4-inch or a 90mm.


How to Find the Right/Perfect Pipe Fitting

Finding the perfect/right pipe fitting can be somewhat challenging. You need to find a fitting with an inside diameter that is just large enough to fit perfectly around your pipe. This is why it is important to know the nominal size of the pipe, as this will enable you to find accurate fittings.

Any time you want to purchase fittings, let your buying decision be based primarily on the nominal size instead of the inner or outer diameter of the pipe.


Other Pipe Measurement Considerations

Another crucial factor to bear in mind is that tubing and piping are measured differently. You cannot use the same methods you employ for measuring pipe fittings for measuring tubing. This is because the latter is measured based primarily on the actual diameter of the tube.

This is because cross-linked polyethylene tubing (PEX) is becoming increasingly common in different settings. PEX is also named and measured differently than standard piping. This is important in case you need to replace PEX tubing.

Remember that you also need to select the thread type alongside the proper nominal diameter for your piping. NPT (national pipe thread) is possibly the most common and often features tapered threads for sealing and joining pipes.

However, other pipe threads could have different advantages for different types of joints. Ensure you choose the right type for the specific application you have in mind.



The first step to carrying out a perfect and successful piping project involves knowing detailed practical information or the nuts and bolts of your equipment.

The second most important step is purchasing high-quality pipe stopples to ensure the success of your piping projects. You need to know how to measure nominal pipe sizes and fittings, as the data obtained will help guarantee the overall success of all the piping projects you handle.

It is also important to remember that the inch/imperial and metric sizes are 2 different systems. The ambiguity of fitting sizes could save you lots of money and time.



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