How To Measure Pipe Size?

How To Measure Pipe Size?

What You Should Know For Pipe Measurements?

Before reading the pipe size chart, we need to understand the different measurements or dimensions listed.

Length: This value is self-explanatory – it represents the length of a section of pipe, usually expressed in standard increments.

Inside Diameter (ID): The inside diameter is the distance between the inside walls. Think of it as the width of the pipe opening.

Outside Diameter (OD): The outside diameter is the distance from the outside edge to its opposite outside edge. Think of it as the overall “height” of the pipe.

Wall Thickness (WT): Similar to length, this value is self-explanatory and is the thickness of the pipe wall. It is also half the difference between OD and ID. Wall thickness is often referred to as a “schedule” which is a non-dimensional number that requires the use of a table to convert it to actual wall thickness.

Nominal Pipe Size (NPS): This is the most commonly used measurement to convey the “size” of a pipe. However, when the NPS is between ⅛” and 12”, it is neither ID nor OD. This means that, while close to the actual diameter of the pipe, it’s another non-dimensional number and more of a designation rather than a measurement. Above 14” (or NPS 14), the nominal pipe size and OD are the same.

For example, below is a table of NPS values from ½” to 3 ½” with their corresponding outside diameter:

Nominal Pipe Size (NPS)	Outside Diameter (OD)
½”	0.84”
¾”	1.05”
1”	1.315”
1 ¼”	1.66”
1 ½”	1.9”
2”	2.375”
2 ½”	2.875”
3”	3.5”
3 ½”	4”

Does Pipe Size Refer To Insisde Or Outside Diameter?

Pipe was originally used to carry water, so the ID (inside diameter) is the critical dimension. The nominal pipe size is ID. Therefore, a 1½ inch pipe does not have an outside diameter of 1½ inches, but rather a nominal inside diameter (approximately) of 1½ inches. Pipe is generally manufactured to looser tolerances and is less expensive to purchase. However, in the fencing and construction industries, where pipes are widely used, they are often expressed in terms of their outside dimensions since fittings, caps, and other parts often fit on the outside of the pipe.

Different Types Of Pipes

So, before we start measuring pipe diameters, we need to understand the different types of pipes you can encounter. Here we will discuss three main categories of pipes: male pipes, female pipes and no thread, and unthreaded pipes. If you are a little confused, let us explain.

Male pipes has a thread located on the outside of the pipe. Female pipes also have a thread but they are located inside the pipe. There are also pipes that do not have threads.

Tapered threads are grooves cut into the ends of pipes to allow them to fit together.

It is important to know the difference between them because each pipe requires different measurements depending on the pipe thread size. So let’s get started.

How To Measure Pipe Size?

Step 1

The first step is to determine whether you are measuring male, female or no thread pipes.. As we said, the male pipe will be identified by the threads on the outside of the edge. Female pipes have similar threads on the inside, and no thread, well they have none. . The thread dimensions will affect the size of the pipe measured.

Of course, not all pipes are created the same, and pipes are made from different types of materials. There is copper pipe, PVC pipe, stainless steel pipe, and cast iron pipe. But nominal pipe sizes apply to all types of pipe, regardless of their material.

Step 2

Now you’ve identified the type of pipe you need to start measuring. The outer diameter of a male pipe with or a no thread pipe is measured from the outside edge of the pipe opening to the opposite outside edge.

Use a flexible tape measure and wrap it around the pipe to get the circumference. Now you need to divide the pipe circumference measurement by pi or 3.14159.

For example, if the circumference measures 12.57 inches, dividing it by pi will give the pipe an outside diameter of 4 inches. If you don’t have a flexible tape measure, you can use the string method to measure pipe fittings.

Wrap a piece of string around the pipe and mark where it meets the starting point of the string.Then hold this against a straight ruler and measure. Divide this by pi to get the outside pipe diameter.

You can of course physically measure the end or cross section of a pipe from one outside edge to the other using a tape measure.Keep in mind that the actual outside diameter of the pipe will be larger than its nominal size.

Step 3

For female pipes, you can measure the inside diameter. You can do this using calipers or a ruler. The inside diameter measurement will be taken from one inside edge to the other inside edge of the pipe cross section.

This measurement does not include the wall thickness. The wall thickness of the pipe is called the wall thickness. The different schedules are 40, 80, and 120. Depending on the purpose of the pipe, you can choose the most suitable nominal size and schedule.

Like the nominal pipe size the schedule is not a precise measurement but a guide to the pipe wall thickness and its best fit for your use.

Step 4

Now you need to take the measurements and convert them to the nominal pipe size. However, this is only necessary if the pipe diameter is less than 14 inches.

Any diameter larger than this size will be the same in terms of diameter and nominal pipe size. It’s important to understand that the nominal pipe sizes are not actual and precise measurements, but a designation applied to pipes.

Step 5

You need determine whether measurements need to be converted to the nominal pipe size (NPS) system or the diameter nominal (DN) system. North America uses the NPS system and the DN system for metric measurements.

The converted numbers will vary for each system. Since NPS is an imperial system, pipe sizes will be in inches or fractions of an inch. It conforms to the standards of the American Society of Mechanical Engineers (ASME).

The DN system is a metric system and conforms to the metric standard of the International Organization for Standardization (ISO). This applies to all pipeline, fuel oil, gas, and other types of pipe.

Step 6

Now you can convert the inside or outside diameter measurement to the appropriate nominal size.This is what your local plumber, tradesman, or building supply store calls pipe size.

There are many tables available online or on the pipe manufacturer’s website to convert measurements. Therefore, to determine the nominal pipe size or nominal diameter, it is necessary to consult a conversion chart.

When you look at these charts, you can see the difference between the actual outside diameter measurement and the nominal pipe size.

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